Download The Digestive System

The Digestive System
Chapter 23
OVERVIEW
•
https://www.youtube.com/watch?v=nM5kMSjBrmw
INTRODUCTION
Digestion is the mechanical and chemical
breakdown of food into forms that cells can absorb.
• Mechanical Digestion – breaks down food into smaller pieces
Chemical Digestion – decomposes food into smaller molecules
•
Add these terms to vocabulary list…
The digestive system consists of:
• The alimentary canal – extends from mouth to anus
•
Accessory glands –secrete chemicals into the alimentary canal.
HUMAN
DIGESTIVE
SYSTEM
THE ALIMENTARY CANAL
If stretched out, the alimentary
canal is about 8 meters long.
That’s 26 feet!
STRUCTURE OF THE WALL
Mucosa – mucous membrane
• Epithelial tissues on a bed of connective tissue
• This layer absorb nutrients, secrete chemicals, and
protect the underlying layers.
Submucosa – Beneath the mucosa
• Loose connective tissue
• Blood vessels, nerves, and lymphatic vessels
• This layer nourishes the surrounding tissues, and carries
away nutrients.
Muscular –
• Decrease and increase the diameter of the
A.C. to push food through
Serosa – serous membrane
• Secretes serous fluid, which lubricates the A.C.
MOVEMENTS OF THE ALIMENTARY CANAL
Muscles of the A.C. provide two basic movements:
Segmentation – mixing
movement
• Smooth muscles contract
and relax, mixing foods with
digestive juices
Peristalsis – propelling movement
• Smooth muscles contract in a
wave-like motion pushing food
through the alimentary canal
THE MOUTH (ORAL CAVITY)
• The mouth:
• Receives food
• Mechanically breaks up solid particles using TEETH & TONGUE
• Chemically digest food using saliva.
• This action is called mastication
• Makes a BOLUS (wet ball of food)
• The mouth also functions as an organ of
speech, and sensory reception.
SALIVARY GLANDS
• Secrete saliva
Saliva moistens the food, and
begins the digestion of
carbohydrates
Three pairs of major
salivary glands,
include:
• Parotid glands
• Submandibular
• Sublingual
SALIVARY GLANDS
SALIVA = water + mucus + amylase
Parotid glands
• Secrete clear watery fluid
• Rich in salivary amylase – begins the chemical digestion of
carbohydrates
Submandibular glands
• Secretes a mixed saliva with both watery fluid
and mucus
Sublingual glands
• Secrete primarily mucus
THE PALATE AND UVULA
• The palate forms the roof of the oral cavity
Hard Palate - bony roof of the mouth
• Formed by the palatine bones and portions of the maxilla
Soft Palate - Muscular arch
Uvula – cone-shaped projection
During swallowing, muscles draw
the soft palate and the uvula
upward preventing food from
entering the nasal cavity.
THE TEETH
Teeth are the hardest structures in
the body
•primary (deciduous) teeth
numbering 20
•Usually erupt through the gums
from age of 6 months to 2 years
•secondary (permanent) teeth
numbering 32
•Usually begin to erupt at 6 years
• 3rd molars = wisdom teeth,
which may erupt between 17-25
years of age
TYPES OF TEETH
Incisorsblade shaped teeth that bite or cut off
large pieces of food
Adult – 8
Child – 8
Caninescone shaped teeth that grasp and tear food
Adult – 4
Child – 4
Premolars –
flattened surface for grinding food
Adult – 8
Child – 0
Molars –
flattened surface for grinding food
Adult – 12
Child – 8
THE TONGUE
• Thick, muscular organ
• Manipulate foods and
aids in swallowing
Mucous Membrane
Frenulum
Root
• Anchored to the hyoid bone.
• Covered with lingual tonsils
Papillae – projections on the surface of the tongue.
• Some provide friction, others house taste buds.
PHARYNX
• The back of the
throat.
• Deglutition
(swallowing)
• 3 parts
SWALLOWING
• Epiglottis
• flap of cartilage
• closes trachea (windpipe) when swallowing
• food travels down esophagus
ESOPHAGUS
• Peristalsis
• involuntary muscle
contractions to move
food along
• Esophageal Hiatus –
opening in the diaphragm,
passage for esophagus
• Hiatal hernia – part of the
stomach protrudes through
the hiatus.
STOMACH
• 2 sphincters (valves)
• 3 layers of muscle
• Secretes gastric juices
(enzymes + HCl)
• Mechanically and
chemically breaks
down food
STOMACH
• Fundus = top portion
• Pyloris = funnelshaped lower portion
• Rugae – gastric folds
line the stomach
GASTRIC JUICE
• Acidic (pH 1.5-2.5)
(HCl)
• Pepsin- an enzyme
that breaks down
large proteins into
amino acids.
• HCl activates pepsin
• BOLUS + GASTRIC
JUICE = chyme.
ACCESSORY ORGANS
•Pancreas
•Gall Bladder
•Liver
PANCREAS
• An organ which secretes both digestive enzymes
(exocrine) and hormones (endocrine)
• Pancreatic juice digests all major nutrient types.
• “ENZYME COCKTAIL” includes enzymes top break down all compounds:
proteins, lipids and carbohydrates
• Alkaline (base) neutralizes acidic chyme coming from stomach.
PANCREAS
LIVER
LIVER FUNCTIONS
• The liver carries on many important metabolic activities, including:
• Glycogenesis: producing glycogen from glucose
• Glycolysis: breakdown of glycogen into glucose
• Gluconeogenesis: converts non-carbohydrates to glucose
• Oxidizes fatty acids
• Synthesizes phospholipids and cholesterol
• Forms urea
• Synthesizes plasma proteins
•Stores glycogen, iron, and vitamins A, D, and B12
• Phagocytosis of worn out RBCs and foreign substances
• Removes toxins such as alcohol and certain drugs from the blood
LIVER
• Function: produces bile
• BILE breaks up fats
GALL BLADDER
• It stores bile between meals
• It concentrates bile by reabsorbing water
• The gall bladder itself does not produce bile
• Bile duct –
• a long tube that carries BILE
• Connects the liver, pancreas, and gall bladder to the
duodenum (small intestine)
GALLSTONES
• GALLSTONES – an accumulation of hardened
cholesterol and/or calcium deposits in the
gallbladder
• Can either be “passed” (OUCH!!) or surgically
removed
SMALL INTESTINE
• Function
• chemical digestion
• major organ of digestion &
absorption
• absorption through lining
• over 6 meters!
• small intestine has huge
surface area = 300m2 (~size
of tennis court)
• Structure
• 3 sections
• duodenum = most
digestion
• jejunum = absorption of
nutrients & water
• ileum = absorption of
nutrients & water
DUODENUM
• 1st section of small intestines
• acid food from stomach
• mixes with digestive juices from:
 pancreas
 liver
 gall
bladder
ABSORPTION IN THE SI
•
Much absorption is thought to occur directly through
the wall without the need for special adaptations
•
Almost 90% of our daily fluid intake is absorbed in the
small intestine.
•
Villi - increase the surface area of the small intestines,
thus providing better absorption of materials
Villi increase surface area.
More surface area = More absorption
APPENDIX
Vestigial organ
APPENDICITIS
• inflammation of the appendix due to infection
• Common treatment is removal of the appendix via
surgery
THE LARGE INTESTINE
The large intestine is named because of its diameter
It has four parts:
1.
Cecum – blind pouch
• Ileocecal sphincter
• The appendix projects from the cecum.
2.
Colon
(ascending, transverse, descending, sigmoid)
3.
Rectum straight
4.
Anal canal
• The anus – is guarded by two sphincter muscles
• external anal sphincter – composed of skeletal muscle
• internal anal sphincter – composed of smooth muscle
LARGE INTESTINES
(COLON)
• Function
• re-absorb water
• use ~9 liters of water every
day in digestive juices
• > 90% of water reabsorbed
LARGE INTESTINE
• Solid materials pass through
the large intestine.
• These are undigestible solids
(fibers).
• Water is absorbed.
• Vitamins K and B are
reabsorbed with the water.
• Rectum- solid wastes exit the
body.
FECES
• Poop, excrement, solid waste, etc…
• Feces is composed of materials not digested or absorbed, and
include: Water, Electrolytes, Mucus, Bacteria, and Bile
pigments
• Approximately 1/3 of the dry weight of feces is bacteria.
.
• The color of feces is provided by bile pigments altered by
bacteria
DIARRHEA
• a gastrointestinal
disturbance characterized
by decreased water
absorption and increased
peristaltic activity of the
large intestine.
• This results in increased,
multiple, watery feces.
• This condition may result in
severe dehydration,
especially in infants
CONSTIPATION
• a condition in which the
large intestine is emptied
with difficulty.
• Too much water is
reabsorbed
• Solid waste hardens
BACTERIAL FLORA
• Living in the large intestine is
a community of helpful
bacteria
• Escherichia coli (E. coli)
• produce vitamins
• vitamin K; B vitamins
• generate gases
• by-product of bacterial
metabolism
• methane, hydrogen sulfide
RECTUM
• Last section of colon
(large intestines)
• eliminate feces
• undigested
materials
• extracellular
waste
• mainly cellulose
from plants
• roughage or
fiber
• masses of
bacteria
ANAL CANAL / ANUS… LAST STOP
• Exit or opening for solid
wastes
• Regulated by anal
sphincter (valve)
• Anal sphincter surrounded
by muscles
• Elimination aided by
abdominal muscles
HEMORRHOIDS
•Very common, especially during pregnancy and after
childbirth.
•Result from increased pressure in the veins of the anus. The
pressure causes the veins to bulge and expand, making them
painful, particularly when you are sitting..
Symptoms
Pain during bowel
• Anal itching
movements
• Anal ache or pain,
One or more hard
tender lumps near the
especially while sitting
anus
• Bright red blood on
toilet tissue, stool, or
in the toilet bowl
EPISIOTOMY
This…
NOTEBOOKS
Due Monday, April 14
Must include:
• RESPIRATORY SYSTEM
• DIGESTIVE SYSTEM
• URINARY SYSTEM
See website for DIGESTIVE SYSTEM powerpoint to
help finish notes on chart.