Download 23 Comp Review 4

Digestive System
SALIVARY GLANDS
Produce saliva
–
Names of some salivary glands:
Parotid (largest). Mumps is a virus that attacks here.
Submandibular
Sublingual
–
Functions of salivary glands
To moisten food so you can swallow, especially crackers.
The mucus in the saliva is what moistens the food.
To inhibit growth of bacteria (which like dark, warm, moist
areas). What does this are the antibodies, enzymes, and
macrophages in the saliva.
STRUCTURE OF TOOTH
GINGIVA are the gums
CROWN is the area above the gingiva
ROOT is embedded in a socket in the bone. In the
maxilla, the root can extend into the maxillary sinus.
Damage to the sinus can be a lot of problems.
ENAMEL is the external layer of the tooth. It is stronger
than bone, but does wear out. It is suppose to be ivory
color, not white. Whitening procedures scrape away
outer oxidized layer, to expose the layer underneath,
which is white, but it will oxidize, too.
DENTIN is deep to the enamel. It is like bone, with living
tissues and cells.
PULP CAVITY with PULP is deep to the dentin. It has
blood vessels and nerves.
PERIODONTAL LIGAMENT attaches the tooth to the
bone. It’s like periosteum. Disease of this structure is
the most common cause of tooth loss in adults.
Tooth
Structure
Figure 22.11
Tooth Problems
When bacteria eat away at the enamel, what’s it called?
CAVITY
The dentist removes a larger area where the bacteria
are, and fills it in.
If the cavity extends into the pulp cavity, there is no way
to clean it up. The treatment is to make a big hole,
scrape out the pulp, and fill up the whole thing = ROOT
CANAL. This is a dead tooth, but still there.
Bacteria between the gingiva and tooth causes
inflammation of the gingiva = GINGIVITIS.
When it gets worse, the gingiva pulls away from the
tooth and the bacteria extends down to the periodontal
ligament = PERIODONTITIS. This is the major cause of
tooth loss. The tooth loosens and falls out. That’s why
you need to floss.
Layers of GI Tube
There are four layers:
1. MUCOSA (inner layer). The lining varies from region
to region.
– Epithelium
– Lamina Propria: Loose connective tissue
– Muscularis mucosae: very thin smooth muscle, causes little
twitches within the mucosa.
2. SUBMUCOSA (moderate dense connective tissue).
Lots of elastic fibers, blood vessels, and lymphatic
vessels.
3. MUSCULARIS EXTERNA (smooth muscle layer with
two parts:
– Circular Layer (inner)
– Longitudinal layer (outer)
4. Serosa
Serosa
Mucosa
Muscularis Externa
Submucosa
3. Muscularis Externa
Muscularis Externa is extremely important for
digestion.
It allows for 2 types of actions:
a. PERISTALSIS: a rhythmic contraction to push
something along. This pushes food down by smooth
muscle contraction.
b. SEGMENTATION: A back-and-forth squeezing
of the muscle to grind up food. Food moves forward then
backward a little, then forward again. Function is to
churn up the food inside.
Some areas have thicker smooth muscle = SPHINCTER.
Circular muscles open and closes an opening.
– Controls the flow of food from one region to another.
Layers of GI Tube
4. SEROSA is not in all regions (none in
esophagus).
– Simple squamous epithelium
– Loose connective tissue
– From internal to external, the layers of
this tube are the mucosa, submucosa,
muscularis, serosa.
Esophagus
Extends from the oropharynx to the stomach,
about 25 cm long. The things that are
specialized in the esophagus are:
1. MUCOSAL EPITHELIUM (non-keratinized
stratified squamous epithelium).
Why? It protects against things you swallow;
pointy potato chips, etc. Cuboidal would slough.
2. MUSCULARIS EXTERNUM in upper half =
skeletal muscle. Lower half = smooth muscle.
Why? The upper half, skeletal muscle, is under
voluntary control. Smooth muscle is not
voluntary. Food gets caught in the lower half
because it hasn’t started peristalsis.
Cardiac Sphincter
The esophagus goes through the thoracic
cavity.
It needs to go through the diaphragm’s
opening (esophageal hiatus).
It empties to the stomach through a
CARDIAC SPHINCTER = a thickening of
the muscularis externa. This is NOT A
TRUE SPHINCTER.
Stomach Anatomy
Stomach: Functions
Store Food
Mechanically churns food into a paste
called CHYME
Kill bacteria
Some digestion: of proteins
Some absorption: of water, alcohol
Gastric emptying is the release of food from the stomach
into the duodenum; the process is tightly controlled with
liquids being emptied much more quickly than solids.
STOMACH FUNCTIONS
1. Store Food, so it can be slowly released into a small
intestine. Your whole Thanksgiving dinner can take your
stomach diameter from 2” to 8” diameter.
2. Mechanically Churns food. Secretions from the
stomach is added, turns everything into a gooey paste.
When you throw up, you can see the enzyme secretions
= CHYME.
3. Kill bacteria. The stomach is very acidic (pH 1) like
battery acid. Chyme will even eat through clothing.
4. Some digestion: of proteins.
5. Some absorption: of water, alcohol (alcohol is
absorbed in the mouth, too!)
Food takes four hours to completely leave the stomach.
The Stomach
Figure 22.15a-c
Stomach Cells
PARIETAL CELLS in the stomach secrete
hydrochloric acid and digestive enzymes which
kill bacteria in the stomach.
They also secrete intrinsic factor, which is
needed to absorb vitamin B12.
CHIEF CELLS secrete an enzyme called
pepsinogen. When pepsinogen is exposed to
hydrochloric acid (HCl), it is cleaved into pepsin,
its active form. Pepsin digests proteins.
Intrinsic Factor
The parietal cells in the stomach secrete a
substance called INTRINSIC FACTOR.
Vitamin B12 requires intrinsic factor in order to
be absorbed.
A person who lacks intrinsic factor (such as
those who have a stomach stapling procedure or
gastric bypass) will not be able to absorb vitamin
B12 and they will get a type of anemia called
pernicious anemia.
Treatment is injectable B12 shots monthly for
the rest of their lives.
Gastric
gland
Figure 22.15a-c
Two major causes
of Peptic Ulcers:
1) 60% of gastric and up to 90% of duodenal ulcers are
due to a bacterium called Helicobacter pylori.
– The body responds by increasing gastrin secretion,
which erodes the stomach lining.
2) NSAIDs (non-steroidal anti-inflammatory drugs, such
as aspirin) block prostaglandin synthesis.
– Prostaglandins promote the inflammatory reaction.
They also are found in the stomach, protecting it from
erosion.
19
Problems With the Stomach
The cardiac sphincter doesn’t close well, since it
is not a true sphincter; consequences:
– You can throw up (reverse peristalsis). Rats do have
a true cardiac sphincter, and can’t vomit!
– That’s why rat poison won’t kill people or dogs; they
can throw it up.
Another consequence: hiatal hernia.
HIATAL HERNIA
Part of the stomach, protrudes through
esophageal hiatus, causing pain and
difficulty swallowing.
It is the most common of all hernias.
There is a great amount of acid reflux;
erodes walls of esophagus, causing
ulcerations of esophagus.
Treatment is surgical; pull down the
stomach, and tighten the hernia in a
laparoscopic procedure.
The Small Intestine
Crypt of Lieberkuhn
Figure 22.17a-c
Small Intestine Regions
Duodenum “12 finger widths long”
Jejunum “hungry when empty”
Ileum “twisted”
DUODENUM
This is the shortest region, only one foot
long.
It receives chyme from the stomach. This
is where digestion begins. There are two
ducts at the beginning of the duodenum
from the pancreas and gallbladder. It is
the site of action of liver secretions (bile)
and pancreas secretions (digestive
enzymes and bicarbonate).
Pancreas
PANCREAS is an endocrine gland, and also
participates in digestion. Most of the digestive
enzymes are made here. They go out the
PANCREATIC DUCT to enter the small
intestine.
It also produces BICARBONATE (from a
hormone called SECRETIN) to increase the pH
(decrease the acidity) of the chyme coming from
the stomach. If there is too much acid there, get
a DUODENAL ULCER.
PANCREAS
ACINAR CELLS: secretes digestive
enzymes
ISLETS OF LANGERHANS: secretes
insulin and glucagon
Pancreas
Acinar cells
(secrete
enzymes)
Islet of
Langerhans
(secretes
insulin and
glucagon)
GALL BLADDER
This is located inferior to the liver, and its
function is to store and concentrate bile.
Bile is a detergent/soap (not an enzyme) which
emulsifies fat: It breaks down the fat into
microscopic droplets which can be broken down
by pancreatic enzymes.
It does NOT make or secrete bile; that is done
by the liver.
Bile is made in the liver from Hemoglobin (Hgb),
and also contains cholesterol and other things.
The function of bile is to break down lipids (fats)
so they can be digested.
Jejunum
JEJUNUM (“empty”)
This is the part of the small intestine where
most digestion and absorption occurs.
It is 3 feet long.
Ileum
ILEUM (“twisted”) is 5-10 feet long. It is
the terminal portion of the small intestine.
Much of the absorption takes place here.
Crypt of Lieberkuhn
Lacteal
Crypt of Lieberkuhn
Figure 22.17a-c
Absorption in Small Intestine
In the villis is a fenestrated capillary bed, which
needs to absorb a lot of material.
The small intestine absorbs carbohydrates, fats,
and proteins (although protein enzymes have
already begun working earlier in the digestive
tract in the stomach).
The walls of the small intestine secrete most of
the digestive enzymes that are active in its
lumen.
Lymphatics of Small Intestine
There are also large lymphatic capillaries
in each villis called LACTEALS, whose
function is to absorb breakdown products
of fat. The vessel is large so it won’t get
clogged up.
Under all this are the MUSCULARIS
MUCOSA muscles which can twitch to
move the villa so food does not get stuck.
Problem with Small Intestine
Crohn’s Disease
– Autoimmune disease of the GI tract
– Most common area affected is small intestine
Celiac disease
(Sprue; gluten intolerance)
Large Intestine
(Colon, or large bowel)
This is about 5 feet long, diameter of 4”.
Absorbs a LOT of water and salts
Absorbs electrolytes (Na, K, etc)
Stores feces for defecation (terminal portion)
Contains abundant bacteria (E. coli):
–
–
–
–
Make vitamins (B5, K, biotin)
Allow material to move through large intestine easier
Keep out harmful bacteria
They eat things you can’t digest
Fiber
Some sugars that we don’t have enzymes for
Regions of the Large Intestine
Cecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anus
Large Intestine
Figure 22.18a
Problems with Large Intestine
DIVERTICULITITS
INFLAMMATORY BOWEL DISEASE
– Crohn’s Disease
– Ulcerative colitis
IRRITABLE BOWEL SYNDROME
COLON CANCER
– SIGMOIDOSCOPY or a COLONOSCOPY
POLYPS
HEMORRHOIDS
DIVERTICULITITS
DIVERTICULUM (Diverticula is plural) can
form, a small pouch in the large intestine.
They can become inflamed, usually from a
small, hard piece of feces, causes the
condition known as DIVERTICULITITS.
These are painful and often need to be
surgically removed.
May be caused by lack of fiber, causing
increased pressure in the colon.
Inflammatory Bowel Disease (IBD)
IBD is a group of inflammatory conditions
of the colon and small intestine.
The major types of IBD are Crohn's
disease and ulcerative colitis
IRRITABLE BOWEL SYNDROME (IBS)
IBS is a diagnosis of exclusion.
Symptoms are chronic abdominal pain, bloating,
and alteration of bowel habits in the absence of
any detectable organic cause.
May manifest as diarrhea or constipation or may
alternate between the two.
May be caused by infection, stress, or onset of
maturity
No cure; treatments attempt to relieve
symptoms, including dietary adjustments,
medication and psychological interventions.
COLON CANCER
This is the #1 most deadly cancer (kills more
people) because it metastasizes and there are
no symptoms. It can be diagnosed by seeing
blood in the stool; this is an easy test, but not
very accurate.
A more accurate test is a SIGMOIDOSCOPY. A
tube is inserted into the sigmoid colon, done in
the doctor’s office. The tube has a light, and
they look for growths on the walls of the intestine
= POLYPS, which are pre-cancerous growths.
A colonoscopy is done under general anesthesia
since the tube has to go through the entire
colon, but it’s more effective.
Hepatic Portal System
Almost all of the blood coming from the digestive
system drains into a special venous circulation
called the portal circulation.
Before these absorbed substances can go into
the systemic circulation (the main blood
circulation in the body), it must be filtered first to
remove or detoxify toxic substances first.
This filtering and detoxification is one of the 500+
functions of the liver.
Liver
Makes blood
Makes blood proteins (clotting factors)
Makes bile
Regulates glucose levels
Processes fats
Makes cholesterol
Processes amino acids
Detoxifies chemicals
Liver
Hepatic
Triad: Vein,
Artery, Bile
Duct
Figure 22.23a, c, d
Liver: sinusoids and hepatocytes
Blood Flow in the Liver
Blood flow to the liver is unique in that it receives both
oxygenated and deoxygenated blood.
Nutrient-rich, oxygen-poor blood from the intestine
enters the liver by the hepatic portal vein. It flows
through the sinusoids for detoxification.
Oxygen-rich blood enters the liver by the hepatic artery.
It flows through the sinusoids to supply them with
oxygen.
All of the blood mixes together, and when the oxygen
demand of the hepatocytes is satisfied, and the toxins
have been removed, the oxygen-depleted blood collects
in a central vein within each lobule, which drains into the
hepatic vein. The hepatic vein subsequently drains into
the inferior vena cava and back to the heart.
Function of Hepatocytes
Detoxification of poisons
Picking up and processing of nutrients
from the portal blood
– This includes picking up glucose from the
nutrient-rich blood coming from the small
intestine and stores it as glycogen (the
storage form of glucose) for when the body
needs it later.
Storage of some vitamins
Kupffer Cells
Within the sinusoids are KUPFFER CELLS,
which are macrophages. As blood flows through
the sinusoids, they phagocytize old erythrocytes.
The released Hgb is given to the hepatocytes,
which convert it to bilirubin, one of the main
components of BILE.
Bile flows through a series of channels called the
BILE CANNICULI to the bile duct.
Problems with the Liver
HEPATITIS
CIRRHOSIS
JAUNDICE
Liver Problems
Infection of the liver = HEPATITIS (can be
deadly)
CIRRHOSIS is when the hepatocytes die
and are replaced by connective tissue.
This is often from alcoholism, which kills
the hepatocytes.
Jaundice
One of the symptoms from any liver
disorder is a connection of the bile
canaliculi and the sinusoid so some
bilirubin can enter the blood.
Bilirubin is yellow-green (later in its
degradation it will turn brown and that is
what gives the feces its color).
The yellow color of bilirubin in the skin is
known as JAUNDICE.
GREATER OMENTUM
GREATER OMENTUM is flat, and is in
front of the intestines like an apron. Its
function is to store fat, especially in
men.
GI Physiology
Part 1: Metabolic Pathways
Part 2: GI Physiology
56
Simple and Complex
Carbohydrates
There are three main simple sugars (AKA
monosaccharides or simple
carbohydrates)
– Glucose
– Fructose
– Galactose
If you join a glucose to any of these, you
get a disaccharide
– Glucose + Glucose = Maltose
– Glucose + Galactose = Lactose
57
Simple and Complex
Carbohydrates
If you join many monosaccharides and/or
disaccharides together, it is called a
polysaccharide (AKA complex
carbohydrate).
These are stored in the liver as glycogen.
They can be broken down later into
glucose as needed.
The storage form in plants is called starch.
When we eat starch, we covert it to
glycogen and then store it.
58
Glucagon and Insulin
Glucagon, a hormone secreted by the pancreas, raises blood glucose
levels.
Its effect is opposite that of insulin, which lowers blood glucose levels.
The pancreas releases glucagon when blood sugar (glucose) levels
fall too low.
Glucagon causes the liver to beak down the stored glycogen into
glucose, which is released into the bloodstream. Since glycogen is
being broken down, this process is called glycogenolysis. Don’t
confuse this with glycolysis (break down of glucose to ATP)!
High blood glucose levels stimulate the release of insulin.
Insulin allows glucose to be taken up and used by insulin-dependent
tissues.
Thus, glucagon and insulin are part of a feedback system that keeps
blood glucose levels at a stable level.
59
Glycolysis
Glycolysis is the process where cells take in glucose and
break it down into pyruvate, and ATP is released.
This is how we get ATP from glucose.
Fructose and galactose can also be broken down into
pyruvate and ATP.
During glycolysis, NAD (an energy molecule) is reduced
to NADH. If you run out of NAD, glycolysis will stop.
Therefore, we need to oxidize NADH to convert it back
into NAD.
This can be done by aerobic or anaerobic respiration, or
fermentation.
60
Aerobic vs. Anaerobic Respiration
Aerobic respiration
(in the
mitochondria)will
result in 6 ATP’s.
Anaerobic
respiration (in our
cytoplasm) will
result in only 2
ATP’s.
More importantly, we get our NAD back, so glycolysis can continue.
61
Making ATP by Aerobic
Respiration
Takes place in the mitochondria
Requires oxygen
Breaks down glucose to produce ATP
Waste products are CO2 and H2O (we exhale them)
The good thing about making ATP from our mitochondria
is that we can make a LOT of it.
The bad things are that it takes longer to make it, and it
requires oxygen, and a muscle cell may have used up all
the oxygen during a sprinting run.
Making ATP by Anaerobic
Respiration
Takes place in the cytoplasm
Does not require oxygen
Breaks down glucose to produce ATP
Waste product is lactic acid
The good thing about making ATP this
way is that we can make it FAST.
The bad thing is that it does not make
much ATP, and we deplete the reserves
quickly.
Lactic Acid Build-up
During strenuous workouts where oxygen becomes deficient, the
pyruvate product of glycolysis does not have enough oxygen to use
for aerobic respiration, so it has to undergo anaerobic respiration.
The enzyme lactate dehydrogenase (LDH) is used to transfer
hydrogen from the NADH molecule to the pyruvate molecule.
Pyruvate with the extra hydrogen is called lactate.
Lactic acid is formed from lactate. This causes muscle aches and
fatigue.
Lactic acid is deactivated by the addition of oxygen to it. Therefore,
breathing heavily adds the oxygen to our system to deactivate lactic
acid, and the muscle pains go away. Warm water or ultrasound will
also increase oxygenated blood to the muscles, easing muscle
cramps from lactic acid.
64
ATP and Creatinine Phosphate
What do we do when we run out of ATP?
Muscle fibers cannot stockpile ATP in preparation for
future periods of activity.
However, they can store another high energy molecule
called creatinine phosphate.
Creatine phosphate is made from the excess ATP that we
accumulate when we are resting.
During short periods of intense exercise, the small
reserves of ATP existing in a cell are used first.
Then creatinine phosphate is broken down to produce
ATP.
Aerobic vs. Anaerobic
Respiration
When do we use aerobic respiration?
– Resting (can breathe easily)
– Running marathons (can breathe easily on long
runs)
Marathon runners want to make sure there will be
enough readily available energy for the muscles, so
they eat a lot of carbohydrates over a two-day
period before the marathon. That’s why they load up
on pasta before a marathon.
When do we use anaerobic respiration?
– Sprint running (can’t talk while sprinting!)
Gluconeogenesis
Gluconeogenesis is a metabolic pathway that results in
the generation of new glucose from non-carbohydrate
carbon substrates such as lactate, glycerol, and amino
acids. Therefore, if we do not have enough glucose in
our body, we will break down proteins (muscles) to make
glucose.
It is one of the two main mechanisms to keep blood
glucose levels from dropping too low (hypoglycemia).
The other means of maintaining blood glucose levels is
through the degradation of glycogen (glycogenolysis).
67
Part 2
GI Physiology
Figure 62-1; Guyton & Hall
68
Saliva
The saliva serves to clean the oral cavity
and moisten the food.
It also contains digestive enzymes such as
salivary amylase, which aids in the
chemical breakdown of polysaccharides
such as starch into disaccharides such as
maltose.
It also contains mucus, a glycoprotein
which helps soften the food and form it
into a bolus.
69
Stomach
The stomach is responsible for the digestion of protein
and ionization of minerals.
Mucous cells (in the stomach) secrete mucous. The
pancreas secretes bicarbonate. Mucous, bicarbonate,
and prostaglandins protect the stomach lining from being
digested.
The parietal cells of the stomach secrete hydrochloric
acid (gastric acid) and intrinsic factor.
Hydrochloric acid (HCl), along with pepsin (from the chief
cells), breaks down proteins to their individual amino
acids.
70
Stomach Protection and
Damage
Downloaded from: StudentConsult (on 23 April 2010 06:51 PM)
© 2005 Elsevier
Downloaded from: StudentConsult (on 23 April 2010 06:51 PM)
© 2005 Elsevier
© 2005 Elsevier
Stomach Acid
The acid itself does not break down food
molecules.
It provides an optimum pH for the activation of
pepsin, and kills many microorganisms that are
ingested with the food.
It can also denature proteins.
The parietal cells of the stomach also secrete a
glycoprotein called intrinsic factor, which enables
the absorption of vitamin B-12.
74
Stomach Acid Diseases
Hypochlorhydria
Hyperchlorhydria
75
Small Intestine
Duodenum
– Absorption of minerals
– Receives pancreatic digestive enzymes
– Secretes hormones when acidic chyme enters duodenum
Secretin
– Tells pancreas to secrete bicarbonate
– Tells liver to make bile
Cholecystokinin (CCK)
– Tells pancreas to release protein-digesting enzymes
– Tells the gallbladder to release stored bile.
– Therefore, it stimulates digestion of fat and protein.
GIP
– stimulates insulin secretion
Motilin
– Initiates peristalsis (increases GI motility)
– Tells the Chief cells to secrete pepsinogen
– Secretes enzymes to break down polysaccharides
Maltase: breaks maltose down into glucose
Lactase: breaks lactose down to galactose plus glucose
Sucrase: breaks sucrose down into fructose plus glucose
76
Small Intestine
Duodenum
– When there is no more chyme entering the
duodenum, it secretes glucose-dependent
insulinotropic peptide (GIP).
– GIP is synthesized by K cells, which are found in the
duodenum and jejunum.
– GIP stimulates insulin secretion.
– Insulin is in the blood stream. It takes the absorbed
sugars and pulls them into cells that need it.
– GIP also stimulates lipoprotein lipase activity in
adipocytes. This causes fat to be broken down into
fatty acids.
77
Lipid digestion and absorption
• Lipid digestion utilizes lingual
and pancreatic lipases, to
release fatty acids and
monoglycerides.
– Bile salts improve chemical
digestion by emulsifying lipid
drops
– Lipid-bile salt complexes called
micelles are formed
78
Fatty Acid
Absorption
• Fatty acids and monoglycerides
enter intestinal cells via diffusion;
bile salts can be reused to ferry
more monoglycerides
• They are combined with proteins
within the cells
• Resulting chylomicrons are
extruded
• They enter lacteals and are
transported to the circulation via
lymph
79
Small Intestine
Jejunum
– Absorbs water-soluble vitamins,
protein and carbohydrates.
– The proteins began to be broken
down into amino acids in the
stomach by pepsin and acid.
– Proteins are further broken down
into amino acids in the duodenum
by trypsin and chymotrypsin (made
by the pancreas and secreted into
the duodenum).
– The carbohydrates are broken
down in the duodenum by
enzymes from the pancreas and
liver into sugars.
80
Small Intestine
Ileum
– Absorbs fat-soluble vitamins, fat, cholesterol,
and bile salts.
– Fats are broken down into fatty acids in the
duodenum.
First, bile emulsifies the fat (breaks it down into
droplets).
Then, lipase (made in the pancreas) breaks the fat
into fatty acids, which are small enough to be
absorbed.
81
Pancreas Enzymes
The pancreas secretes about one and a half liters of
pancreatic juice a day!
Pancreatic juice secretion is regulated by the hormones
secretin and cholecystokinin, which is produced by the
walls of the duodenum upon detection of acid food,
proteins and fats.
The enzymes produced by the pancreas include
– Lipases
– Amylases
– Proteases
82
Pancreas Enzymes
Lipases
– Digestion of fats, oils, and fat-soluble vitamins
Amylases
– Break down starch molecules into smaller sugars.
– Break down carbohydrates into maltose
Proteases
– Break down protein into smaller amino acids
– Proteases include trypsin, chromotrypsin and carboxypeptidase.
– Proteases are also responsible for keeping the small intestine free
from parasites (intestinal worms, yeast overgrowth and bacteria).
– A lack of proteases can cause incomplete digestion that can lead
to allergies and the formation of toxins.
83
Regulation of Pancreatic Secretion
• Secretin and CCK are released
when fatty or acidic chyme enters
the duodenum
• CCK and secretin enter the
bloodstream
• Upon reaching the pancreas:
– CCK induces the secretion of
enzyme-rich pancreatic juice
– Secretin causes secretion of
bicarbonate-rich pancreatic juice
• Vagal stimulation also causes
release of pancreatic juice
84
The Pancreas
Exocrine function (98%)
– Acinar cells make, store,
and secrete pancreatic
enzymes
Endocrine function –
–  cells (delta cells) release
somatostatin (inhibitory to
gastrin and insulin and
glucagon)
– β-cells –release insulin
– α-cells-Release glucagon
85
The Pancreas as an Endocrine
Gland
Insulin
– Beta cells
– Promotes glucose uptake
– Prevents fat and glycogen
breakdown and inhibits
gluconeogenesis
– Increases protein synthesis
– Promotes fat storage
Epi/Norepi inhibit insulin!
Help maintain glucose levels during
times of stress and increase lipase
activity in order to conserve glucose
levels
Picture from:http://www.dkimages.com/discover/Home/Health-and-Beauty/Human-Body/Endocrine-System/Pancreas/Pancreas-1.html
86
The Pancreas as an Endocrine
Gland
Glucagon
– Increases blood glucose levels
– Maintains blood glucose between
meals and during periods of
fasting by breaking down
glycogen (stored in liver) into
glucose.
– Initiates glycogenolysis in liver
(within minutes).
– Stimulates gluconeogenesis. This
process involves breaking down
amino acids (proteins) into
glucose.
– Stimulates amino acid transport to
liver to stimulate gluconeogenesis
– Nervous tissue (brain) does not
need insulin; but is heavily
dependent on glucose levels!
Image from: http://www.dkimages.com/discover/previews/768/74261.JPG
87
Liver and Gallbladder
The liver produces bile that is either stored by the
gallbladder or secreted into the small intestine.
– Bile emulsifies fats and fat-soluble vitamins.
– It also helps keep the small intestine free from
parasites.
The liver does not make the digestive enzymes for
carbohydrates, amino acids and proteins (the pancreas
and small intestine do that), but the liver does metabolize
proteins, carbohydrates and cholesterol.
It also is responsible for the detoxification of toxins,
drugs and hormones.
88
Large Intestine
The large intestine absorbs water,
electrolytes and some of the final products
of digestion.
Food products that cannot go through the
villi, such as cellulose (dietary fiber), are
mixed with other waste products from the
body and become hard and concentrated
feces.
89
Physiology of the large intestine
– Reabsorption of water and
electrolytes
– Coliform bacteria make:
Vitamins – K, biotin, and B5
– Organic wastes are left in the
lumen
90
Phases of gastric secretion
Cephalic phase
Gastric phase
Intestinal phase
91
Cephalic phase
This phase occurs before food enters the stomach and involves
preparation of the body for eating and digestion.
Sight and thought stimulate the cerebral cortex. Taste and smell
stimulus is sent to the hypothalamus and medulla oblongata.
After this it is routed through the vagus nerve and release of
acetylcholine.
Gastric secretion at this phase rises to
40% of maximum rate. Acidity in the
stomach is not buffered by food at this
point and thus acts to inhibit parietal
(secretes acid) and G cell (secretes
gastrin) activity via D cell secretion of
somatostatin.
92
G cell secretion of gastrin
D cell secretion of somatostatin
93
G cells and Gastrin
G cells are found deep within the gastric glands of the stomach.
When food arrives in the stomach, the parasympathetic nervous
system is activated. This causes the vagus nerve to release a
neurotransmitter called Gastrin-releasing peptide onto the G cells in
the stomach.
Gastrin-releasing peptide, as well as the presence of amino acids in
the stomach, stimulates the release of gastrin from the G cells.
Gastrin tells parietal cells to increase HCl secretion, and it also
stimulates other special cells to release histamine.
Gastrin also tells the chief cells to produce pepsinogen.
Gastrin is inhibited by low pH (acid) in the stomach. When enough
acid is present, it turns off.
94
Gastrin
Gastrin is released in response to
– Stomach distension
– Vagus nerve stimulation
– The presence of proteins or amino acids
Gastrin release is inhibited by
– The presence of enough HCl in the stomach
(negative feedback)
– Somatostatin also inhibits the release of
gastrin
95
D cells
D cells can be found in the stomach,
intestine and the Islets of Langerhans in
the pancreas.
When gastrin is present, D cells increase
somatostatin output.
When D cells are stimulated by Ach, they
decrease somatostatin output.
96
Somatostatin
Somatostatin is also known as growth hormone-inhibiting hormone.
It suppresses the release of gastrointestinal hormones
– Gastrin
– Cholecystokinin (CCK)
– Secretin
– GIP
It suppresses the release of pancreatic hormones.
It slows down the digestive process.
It inhibits insulin release.
It inhibits the release of glucagon.
97
Gastric phase
This phase takes 3 to 4 hours. It is stimulated by
distension of the stomach, presence of food in stomach
and decrease in pH.
This activates the release of acetylcholine which
stimulates the release of more gastric juices.
As protein enters the stomach, it binds to hydrogen ions,
which raises the pH of the stomach.
Inhibition of gastrin and gastric acid secretion is lifted.
This triggers G cells to release gastrin, which in turn
stimulates parietal cells to secrete gastric acid.
Acid release is also triggered by acetylcholine and
histamine.
98
Intestinal phase
This phase has 2 opposing actions: the
excitatory and the inhibitory.
Partially digested food fills the duodenum.
This triggers gastrin to be released.
It also triggers the enterogastric reflex,
which inhibits the Vagus nerve.
This activates the sympathetic nervouse
system, which causes the pyloric sphincter
to tighten to prevent more food from
entering the duodenum.
99
Digestive Enzymes
Salivary glands
-amylase
lingual lipase
Stomach
pepsin
Intestinal Mucosa
sucrase
maltase
lactase
Pancreas
amylase
trypsin
chymotrypsin
carboxypeptidase
lipase
cholesterolesterase
100
The Activities of Major Digestive Tract Hormones
101
Figure
24.22
Organ
Pancreas
Region of the Organ
Acinar cells
Acinar cells
Substances
Amylase (enzyme)
Lipase (enzyme)
Acinar cells
Acinar cells
Protease enzymes (trypsin,
chymotrypsin, carboxypeptidase)
Bicarbonate (not an enzyme)
Islet of Langerhans; Alpha
cells
Islet of Langerhans; Beta
cells
Islet of Langerhans; Delta
cells
glucagon (hormone)
insulin (hormone)
Somatostatin (hormone)
Function
Breaks down starch and carbohydrates into glucose
Breaks down fat into fatty acids
Breaks down proteins into amino acids and also kills intestinal parasites
and bacteria
Raises pH in duodenum
Causes glycogenolysis, the process which breaks down glycogen into
glucose to raise blood glucose. Also causes gluconeogenesis to make new
glucose molecules
Removes glucose in bloodstream and brings it into cells. Lowers blood
glucose levels.
Inhibits gastrin, insulin, and glucagon (inhibits digestive system)
Liver
Bile (a detergent)
Salivary glands
Amylase (enzyme)
Stomach
Mucous (not an enzyme)
Protect the stomach lining
Prostaglandins (not an enzyme)
Protect the stomach lining
Breaks down starch and carbohydrates into glucose
Parietal cells
HCl (not an enzyme)
Parietal cells
Intrinsic factor (not an enzyme)
Allows Vit B12 to be absorbed, which is needed to make RBCs. Without it,
you get megaloblastic (pernicous) anemia.
Chief cells
G cells
Pepsinogen --> pepsin (enzyme)
Gastrin (hormone)
Breaks proteins into amino acids
Tells parietal cells to secrete HCl
Duodenum
Secretin (hormone)
CCK (hormone)
K cells
GIP (hormone)
Motilin (hormone)
Allows Pepsinogen to be converted to pepsin, and it also kills bacteria
Tells pancreas to secrete bicarbonate
Tells pancrease to secrete proteases, and tells gallbladder to release
stored bile (stimulates fat and protein digestion)
Tells pancreas to release insulin and also causes fat to be broken down
into fatty acids
Initiates perstalsis and tells Chief cells to secrete pepsinogen
Maltase, Lactase, Sucrase (enzymes) Break down complex carbohydrates into glucose
102
The Ovaries
Small, almond-shaped organs, each 1 ½” x 1”
Within the peritoneal cavity on the posterior body wall
Covered by a superficial epithelium called the VISCERAL
PERITONEUM.
Held in place by mesentery called MESOVARIUM
Also held in place by ligaments
– BROAD LIGAMENT: where the mesentery attaches to the
uterine (fallopian) tube; this is an extension of the mesovarium.
– SUSPENSORY LIGAMENT: holds the ovary superiorly
– OVARIAN LIGAMENT: connects ovary to the uterus
Ovarian arteries – arterial supply through the mesentery to the
ovary
The Female Reproductive
System
Figure 24.11a
Female Internal Reproductive
Organs
Figure 24.10
Ovary
Medulla
Cortex
Tunica albuginia
Primary follicle
Secondary follicle
Graafian follicle
Primary Follicle
• The oocyte is surrounded by a group of cells called
FOLLICULAR CELLS.
• The whole structure is called the PRIMARY
FOLLICLE.
• At puberty there is a change in hormones which
causes development of some of these oocytes.
Primary Follicle
Oocyte
Follicular cells
The Ovarian Cycle
Ovulation – occurs about halfway
through each ovarian cycle
– Oocyte exits from one ovary (it is now
called an ovum)
Enters the peritoneal cavity
– Is swept into the uterine tube
Luteal Phase – occurs after ovulation
– Remaining follicle becomes a corpus
luteum
Secretes progesterone
Acts to prepare for implantation of an embryo
Secondary follicles
with oocyte
The Ovarian
Cycle
Primary follicles with
oocyte
Graafian follicle
with oocyte
ovum
corpus luteum
Figure 24.13
The average ovarian cycle is 28 days.
Day 1
This is the first day of menstruation. The
primary follicle begins to develop.
The female sex cycle begins on the first
day of menstruation.
OVARIAN CYCLE
Day 1-7
The oocyte develops and the follicle cells
grow and divide.
The adenohypophysis secretes FSH
(follicle stimulating hormone). This causes
20-30 eggs to be stimulated in both
ovaries.
Day 1
Day 7
SECONDARY FOLLICLE
It has now become a SECONDARY
FOLLICLE, which starts to produce the
hormone ESTROGEN.
Estrogen causes a build up the lining of
the uterus and also inhibits the
development of the follicles.
Secondary follicles
with oocyte
The Ovarian
Cycle
Primary follicles with
oocyte
Graafian follicle
with oocyte
ovum
corpus luteum
Figure 24.13
Day 14: GRAAFIAN FOLLICLE
The follicle is fully mature = GRAAFIAN
FOLLICLE.
The oocyte is now fully mature = ovum
The ovum is surrounded by a ring called
the CORONA RADIATA.
It is then surrounded by a space =
ANTRUM, which contains a clear fluid.
The antrum is surrounded by the follicular
cells.
OVULATION
The mature follicle is still producing estrogen. It has
become so big that it forms a blister on the outside of
the ovary.
The adenohypophysis secretes another hormone
called LH (leuteinizing hormone).
LH causes fluid to rapidly flow into the antrum, which
then expands and pops, which also breaks through
the tunica albuginia. The egg and corona radiata are
released into the peritoneum. This process is called
OVULATION. Can be some pain.
Ovulation
OVULATION
The follicle cells that are leftover remain
in the ovary and are called the
CORPUS LUTEUM (“yellow body”).
After a pregnancy the corpus luteum
disintegrates into dead tissue; a white
scar called the CORPUS ALBICANS
(“white body”). In autopsy, you can see
how many of these scars are present to
determine the number of pregnancies
she had.
The Ovarian Cycle
CORPUS ALBICANS
corpus luteum
Figure 24.13
Day 14-21
The egg takes a week to make its way
down to the entrance of the uterus.
The follicular cells continue to grow and
now they make progesterone, which builds
the uterus lining so it’s ready for the egg
by the time it gets there.
Ovarian Cycle
Day 23
If no fertilization, the egg starts to break
down.
Day 27
There is no more estrogen.
Day 28
Menstruation starts as the uterine lining
breaks down  Day 1
FERTILITY PILLS
Women who have trouble conceiving take
fertility pills = FSH, which causes 100
follicles to develop, 4-5 of which may
mature  multiple births.
BIRTH CONTROL PILLS
Birth Control Pills are made of estrogen,
so they inhibit the development of the
follicles, but the uterine lining still grows.
They are taken for 3 weeks, then one
week is taken off to allow for menstruation.
Some of the new estrogen pills can cause
a period only every 3 months instead, but
there are side effects.
Estrogen
The estrogen allows for deposition of
subcutaneous fat, which is what gives
women their curves.
In pregnancy, the breasts get larger, the
mammary glands get bigger.
Fertilization
If the egg is fertilized, the corpus luteum
grows until the pregnancy is over and then
disintegrates into the CORPUS
ALBICANS, which is a scar that can be
seen on autopsy; reveals the number of
pregnancies she had.
UTERINE (FALLOPIAN) TUBES
The ovary is in the peritoneal cavity,
surrounded by the peritoneum, with an
egg releasing.
The uterine tube has FIMBRIAE (“fingers”)
that surround the ovary. When the egg is
released, it goes into the peritoneal cavity,
but the CILIA that line the uterine tube
create a current that drags the egg in.
Uterine Tube
UTERINE(FALLOPIAN )
TUBES
The uterine (fallopian) tubes are held up
by the broad ligament and the suspensory
ligament.
The uterine tubes are about 10cm long
(3”), but only 7/10cm in diameter, and the
actual lumen where the tube enters the
uterus is tiny.
The Uterine Tubes
Figure 24.11a
The Uterine Tubes
The uterine tube is made of the INFUNDIBULUM
(funnel), the AMPULLA (most of the tube), and the
ISTHMUS (the part of the tube closest to the uterus).
The ampulla is where fertilization usually occurs. If the
egg implants outside of the uterus or on the external
surface of the wall of the uterus, it is called an ECTOPIC
PREGNANCY. The most common location for an ectopic
pregnancy is the uterine tubes.
ECTOPIC PREGNANCY
The egg is normally fertilized in the uterine tube,
goes down into the uterus and implants there. If it
implants anywhere else, it is called an ECTOPIC
PREGNANCY.
If it implants in the uterine tube = TUBAL
PREGNANCY, a type of ectopic pregnancy.
The uterine tube is the most common location for an
ectopic pregnancy.
Ectopic pregnancies are fatal to the mother and
embryo, but nowadays there are few deaths of the
mother because it is very painful, so she will go to
the ER and they will do surgery.
PELVIC INFLAMMATORY DISEASE
Sperm swim out of the opening of the
uterine tube and into the peritoneal cavity.
That means any STD can also enter there,
causing PELVIC INFLAMMATORY
DISEASE (PID), which is when it spreads
to the ovaries.
It could then continue to all organs in the
pelvis EXCEPT those organs which are
retroperitoneal (Kidney, ureter, and
urethra). It includes SALPINGITIS
(inflammation of the uterine tube).
PID
The most common cause of PID and
infertility in women is STD, usually
Chlamydia or gonorrhea.
The inflammation and scarring closes off
the uterine tube; although PID does not
inhibit ovulation, it can lead to sterility.
UTERUS
Endometrium
UTERUS
It is held in place by by
the ROUND
LIGAMENT and
mesentery = the
BROAD LIGAMENT.
When a woman stands
upright, the uterus sits
on top of the urinary
bladder
The Female Reproductive
System
Figure 24.11a
Layers of the Uterus
ENDOMETRIUM (two layers)
– STRATUM FUNCTIONALE
– STRATUM BASALE: the deeper layer, can
divide and grow to replace itself.
UTERUS
The stratum functionale develops with the
hormone cycle, which causes it to grow,
along with its glands and blood vessels.
When the hormones stop, the stratum
functionale breaks down, leaving only the
stratum basale.
UTERUS
Deep to the endometrium is the
MYOMETRIUM, made of smooth muscles
which contract during birth.
The PERIMETRIUM (Or Epimetrium) is
the name of the visceral perineum.
ENDOMETRIOSIS
Pieces of the endometrium are supposed
to fall down the vagina, but sometimes its
cells go up the uterine tube and enter the
peritoneal cavity.
They can lodge anywhere; on top of the
fundus, even on the lung pleura.
One lady got a collapsed lung every
month!
FIBROIDS
These are benign tumors like scar tissue
in the myometrium. They can get large
and be painful, especially during
contraction of menses and pregnancy.
Fibroids are the most common reason for
hysterectomy (surgical removal of the
uterus).
EXTERNAL GENITALIA = VULVA
Parts of the vulva
MONS PUBIS is a pad of adipose tissue above the pubic
symphysis, covered with pubic hair.
LABIA MAJORA is an extension on either side of the
vestibule, also with pubic hair. It is the female
equivalent of the scrotum.
LABIA MINORA is medial to the labia majora. They are
thin folds of tissue and erectile tissue.
CLITORIS (equivalent of the penis), which also has
erectile tissue. The clitoris is covered by a PREPUCE
and has a CORPORA CAVERNOSA.
The External Genitalia and
Female Perineum
Figure 24.20
EPISIOTOMY
A purpose of an episiotomy during
childbirth is to minimize tearing of the
central tendon and muscles of the pelvic
floor.
Reproductive System Cancers
in Females
Ovarian cancer – arises from cells in the
germinal epithelium
Endometrial cancer – arises from the
endometrium of the uterus
Cervical cancer – slow-growing, arises
from epithelium at the tip of the cervix
Reproductive System Cancers
in Females
Breast cancer – Second most common cause of cancer deaths in
women
97% occurs in women over 50
Usually arises from cells in the milk ducts
When the skin is dimpled from breast cancer, the suspensory
ligaments of the breast are causing the dimpling.
Treatment
–
–
–
–
Surgical removal of the mass (lumpectomy)
Radiation therapy
Administration of selected hormones
Chemotherapy
Embryology
Embryology – study of the origin and
development of single individual
This is an amazing process that one cell
can grow into an entire organism is 9
months! Remember, typical (diploid) cells
of the body have 46 chromosomes; and
each gamete has 23 chromosomes.
-At the moment of conception, you spent about
half an hour as a single cell.
Fertilization
occurs in the
ampulla
portion of the
uterine tube.
The most
common site
of ectopic
pregnancy is
the uterine
tube
Figure 3.3
hCG Hormone
The trophoblast cells secrete a hormone =
hCG (human chorionic gonadotrophin).
This hormone maintains the growth of the
uterine lining. If no hCG is present, there
will be menses.
hCG is the hormone which is measured in
a pregnancy test. It will be in sufficient
quantities to be measured within about
one week after a missed period.
Implantation
CHORIONIC VILLI are projections from
the fetus that burrow into the uterus.
The capillaries within a chorionic
villus of the placenta contain blood
from the fetus only, not the mother.
Therefore, this tissue can be used for
genetic testing for birth defects.
Figure 3.4
FETAL DEVELOPMENT
The heart starts to pump during the fourth week.
Male and female fetuses can first be
distinguished by their genitals at 3 months.
Birth Defects
FETAL ALCOHOL SYNDROME from the
mother drinking alcohol is the most
common cause of mental retardation in the
United States.
The most common birth defects worldwide involve the heart and circulation.
Fetal Alcohol Syndrome
Birth Defects
A TERATOGEN (“monster maker”) is any
chemical, physical, or biological agent that
induces birth defects.
THALIDOMIDE was a medicine used for
morning sickness in the late 1950’s and
early 1960’s until it was found to cause the
babies to be born without arms and legs.
About 20,000 babies in 46 countries were
affected.
Teratogen Affect
EMBRYONIC DEVELOPMENT OF
THE SCROTUM
7 Months in utero
The testis (singular) is retroperitoneal,
located up high, above the pubic
symphysis. The vas deferens comes off it.
A fibrous band = GUBERNACULUM goes
from the pubic symphysis and inserts onto
the skin under the penis.
7 Months
8 Months
The gubernaculum shrinks, and testes are
pulled down. The peritoneum forms a
pouch =VAGINAL PROCESS. The
abdominal muscles come down and goes
around the testes.
8 months
Birth
The vaginal process is pinched off,
forming the TUNICA VAGINALIS.
The vas deferens goes into the abdominal
cavity.
The DARTOS MUSCLE (cutaneous) lines
the scrotum, leading in to the
CREMASTER MUSCLE.
– The function of the cremaster muscle is to
help keep a gonad cool or warm.
Decent of the Gonads
Figure 24.29a-c
Spermatic Cord
Vas deferens (ductus deferens)
Cremaster muscle
Spermatic (testicular) artery and vein
Pampiniform plexus (Nerves and lymphatic
vessels).
The Dartos and cremaster muscles both
elevate the testes in the cold so they can
stay warm, and they relax in the heat to allow
the testes to descend to stay cool.
– Tight underwear can cause a low sperm count
ERECTION IN MALES
The erectile tissue is lined by tissue which
extends into itself, creating vascular
spaces which can fill with blood, causing
the penis to become more rigid and
expand.
The erection is due to vasodilation, with
blood moving into erectile tissue.
The Male Reproductive System
The testes: this is the primary sex organ in
the male, not the penis.
The scrotum – skin and superficial fascia
surrounding the testes
– Positioning provides an environment 3˚ cooler
than body temperature
Dartos muscle – layer of smooth muscle
Cremaster muscle – bands of skeletal muscle
surrounding the testes
– Elevates the testes
Testes
In order for sperm to be produced, the
temperature has to be a few degrees
lower than normal (3˚ cooler).
To insure a lower temperature, the testes
are located outside of the body, in the
scrotum (outside of the pelvis).
The temperature is maintained by muscles
that elevate and depress the testes.
Problems at Birth
1. CONGENITAL INGUINAL HERNIA
– The vaginal process doesn’t close off completely,
and a piece of intestine gets caught there
INGUINAL HERNIA
– If you do heavy lifting, it increases the
abdominal pressure, and a piece of intestine
gets pushed into the opening called the
inguinal canal. Requires surgery.
2. UNDESCENDED TESTES
– Sperm will still be able to exit from the body, male
sex hormones will still circulate in the body, and
the testes will still have adequate blood supply.
However, viable sperm will not be produced.
Needs a surgery to yank them down.
Structure of the Testes
Are enclosed in a serous sac – the tunica
vaginalis
Tunica albuginea – fibrous capsule of the
testes
– Divides each testis into 250-300 lobules
Lobules contain 1-4 coiled seminiferous tubules
The Testes
Figure 24.3a
The Seminiferous Tubules
Seminiferous tubules
– They are 70 cm (2 feet) long.
Function of seminiferous tubules is to
make sperm.
– Spermatogenic cells – sperm-forming cells
– Columnar sustentacular cells – support cells
Interstitial Cells
Between the seminiferous tubules are
groups of cells = INTERSTITIAL CELLS,
which produce testosterone.
Epididymis
The seminiferous tubules come together to form
the EPIDIDYMIS, the tube of which is 5 meters
(the width of this room!).
The function of the epididymis is to allow sperm
to mature and to store them.
It takes 20 days for the sperm to go from
production to storage.
If sperm is not ejaculated, it will just die and be
phagocytyzed.
The epididymis has smooth muscles for
peristalsis during ejaculation to move the sperm
along.
The Epididymis
Tube leading
out of the
epididymis
Figure 24.3a
Spermatic Cord
The SPERMATIC CORD leaves the
epididymus and contains the spermatic
artery, vein, nerves, and the DUCTUS
(VAS) DEFERENS which is the tube that
carries the sperm out of the epididymis.
The Vas deferens is long, 45cm (2 feet).
It goes through the inguinal canal, loops
around urinary bladder and down the other
side. It’s easy to see on a cat.
The Ductus (Vas) Deferens
Figure 24.1
The Spermatic Cord
Figure 24.2
Most common cause of infertility
In spermatic cord is a network of vessels.
The veins there can become varicose =
VERICOCELE. As they expand, there is
less blood flow, temperature drops in
testes leading to infertility.
Second most common cause of infertility is
STD (inflammation blocks vas deferens).
Seminal Vesicles
Posterior to the urinary bladder =
SEMINAL VESICLES
The EJACULATORY DUCT meets up
with the PROSTATIC URETHRA in the
prostate.
Seminal Vesicle
Figure 24.1
Seminal Fluid
The functions of the seminal vesicles
(60%) and the prostrate (40%) are to
produce most of the seminal fluid
(seminal fluid plus sperm = semen).
Functions of the Semen
Medium for sperm to swim in
Nutrients for sperm (fructose)
Neutralizes acidity in vagina to allow
sperm to survive
Prostate
The urethra goes through the
middle of the prostate, and the
prostate continues to grow
throughout life.
PROSTATIC HYPERTROPHY
– Can constrict the urethra, causing
retention of urine because it is hard
to urinate. Needs surgery to open.
Final Journey of the Sperm
The vas deferens picks up fluid from the
prostate, and the semen enters the
urethra.
It picks up more secretions from the
bulbourethral glands.
BULBOURETHRAL GLANDS
At the base of the urethra
Secretes mucous during erection
Function is to lubricate the urethra for
sperm to swim in and neutralize pH from
urine there.
– It allows the semen to flow and survive.
– Only a small amount of fluid is produced.
Review
The testes are the primary sex organ in the
male because it makes the hormone that
creates secondary male sex characteristics.
A male secondary sex characteristic is a
deep voice, facial hair, prominent thyroid
cartilage.
Sperm is made in the testes, goes into the
vas deferens, loops over the urinary bladder,
and goes into the seminal vesicle and
prostate gland.
Bulbourethral Gland
Figure 24.1
Cross-Section of Penis
In cross-section, within the penis there are
three tubes (2 posterior) called
CYLINDERS OF ERECTILE TISSUE.
The posterior two are the CORPUS
CAVERNOSUM (Corpora cavernosa,
plural).
The anterior one is the CORPUS
SPONGIOSUM, within which is the
urethra.
Cross-Section of Penis
The
Penis
Figure 24.8a, b
The Penis
Figure 24.8a, b
Penile Erection
The erectile tissue in the corpora cavernosa
is lined by dense fibrous connective tissue
which extends into itself, creating vascular
spaces which can fill with blood, causing the
penis to become more rigid and expanding.
The erection is due to vasodilation, with
blood moving into erectile bodies (tissue).
The corpus spongiosum doesn’t get as rigid
or it would squeeze urethra shut.
Viagra
Medicine which allows vasodilation, but if
you have heart disease, it can give you a
heart attack.
An erection squeezes the veins shut so
the blood can’t leak out.
If Viagra (or anything else) causes an
erection for longer than four hours (called
priapism), the erection decreases the
blood flow, and the tissue is killed.
Other Problems with the Penis
Hypospadia is the most common
congenital abnormality of the urethra,
and is in males only.
The skin around the urethra does not
close all the way, and the urethra is open
to the outside of the body. It requires
surgical closure within one year of birth.
Hypospadias
Reproductive System Cancers
in Males
Testicular cancer
– Affects 1 of 50,000 males
– Cured in 95% of cases
Prostate cancer
– Slow-growing
– Risk factors
Fatty diet
Genetic predisposition