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Digestion ch34 Mader
p647 #1,2,4,5 7,9, 10
#1 an incomplete digestive tract has a single opening, usually called a
mouth. For example the planarians (flatworms that are carnivorous) have a
mouth and muscular pharynx, the tract (a gastrovascular cavity) branches
throughout the body. They wrap their body around the prey and the
pharynx (which extends beyond the mouth) sucks up minute quantities at a
time. Digestive enzymes allow some extracellular digestion to occur.
Digestion is completed intracellularly by the cells that line the tract. No cell
is far from the tract so diffusion is sufficient to distribute nutrients.
Earthworms (annelids) have a complete digestive tract and feed mainly on
dead organic matter in soil. They have a single opening which is used as
both a mouth an entrance for food (mouth) and an exit for wastes
(anus).Muscular pharynx draws in food with a sucking action. Food enters
crop (storage area with thin expansive walls). Then, food goes to gizzard
and there, thick,muscular walls crush and sand grinds the food. Digestion is
extracellular within an intestine.The surface area of digestive tracts is often
increased for absorption of nutrient molecules, and in earthworms, this is
accomplished by an intestinal fold called the typhlosole. Undigested
remains pass out the anus. The specialized parts are the pharynx, the crop,
the gizzard and the intestine each has a particular function in the digestive
process.
#2 Clams (continuous feeder which are constantly in the process of
digesting whatever they can filter into their bodies) are filter feeders. Water
always moves through the mantle cavity by the incurrent siphon (slitlike
opening) and depositing particles (algae, protozoans, invertebrates)which
adhere on the gills. Ciliary action moves particles that are the right size to
the labial palps, which force them through the mouth into the stomach.
Digestive enzymes are secreted by a digestive gland but amoeboid cells
present throughout the tract are believed to complete the digestive process
by intracellular digestion.
Squids (discontinuous feeders that have storage areas for food for later
digestion) have tentacles with suckers with toothed horny rings that they
use to capture prey (fish, shrimp, worms) to bring it to the beak like jaws,
which bite off pieces with a radula (a tongue-like structure). The esophagus
Digestion ch34 Mader
leads to a stomach and a cecum, where digestion occurs. The stomach and
cecum retain food until digestion is complete.
#4
Digestion ch34 Mader
Notes: Saliva contains salivary amylase to begin the break down of starch
into maltose
The stomach churns and mixes food with mucus and gastric juices to
produce chyme. Pepsin begins protein breakdown.
Duodenum of small intestine receives bile from the liver and pancreatic
juice from the pancreas. Bile emulsifies fat (breaks it into smaller droplets)
to ready it for digestion by an enzyme from pancreas. Pancreas also
produces enzymes that digest starch and protein (see chart that you were
given in class)
Small intestine has small fingerlike projections called villi where nutrient
molecules are absorbed. Amino acids and glucose enter blood vessels of a
villus. Glycerol and fatty acids are packaged as lipoproteins before entering
lymphatic vessels called lacteals in a villus.
Large intestine has no digestive juices. It absorbs water, salts and some
vitamins
Liver receives blood from hepatic portal vein.
#5 Nutrients are absorbed into the vessels of a villus, which contains blood
capillaries and a lymphatic capillary, called a lacteal. Sugars (remnants of
digestion of carbohydrates) and amino acids (from protein) enter the blood
capillaries of a villus. Glycerol and fatty acids (from fats) enter the epithelial
cells of the villi and within these cells, they are joined and packaged as
lipoprotein droplets (chylomicrons), which enter a lacteal. After the are
absorbed, they are eventually carried to all cells of the body by the
bloodstream.
#7 Functions of the Accessory organs: Liver, gall bladder and pancreas
The liver receives blood from two sources. Freshly oxygenated blood is brought to the liver by the common hepatic
artery, a branch of the celiac trunk from the abdominal aorta. Blood that is rich in nutrients from the digestive tract is
carried to the liver by the hepatic portal vein.The liver has a wide variety of functions and many of these are vital to
life.
Digestion ch34 Mader
Liver functions include the following:
•
secretion
•
synthesis of bile salts
•
synthesis of plasma protein
•
storage
•
detoxification
•
excretion
•
carbohyrate metabolism
•
lipid metabolism
•
protein metabolism
•
filtering
GALLBLADDER: The principal function of the gallbladder is to serve as a storage reservoir for bile. Bile is
a yellowish-green fluid produced by liver cells. The main components of bile are water, bile salts, bile
pigments, and cholesterol.Bile salts act as emulsifying agents in the digestion and absorption of fats.
Cholesterol and bile pigments from the breakdown of hemoglobin are excreted from the body in the bile.
PANCREAS: The pancreas has both endocrine and exocrine functions. The endocrine portion consists of
the scattered islets of Langerhans, which secrete the hormones insulin and glucagon into the blood. The
exocrine portion is the major part of the gland. It consists of pancreatic acinar cells that secrete digestive
enzymes into tiny ducts interwoven between the cells. Pancreatic enzymes include anylase, trypsin,
peptidase, and lipase. Pancreatic secretions are controlled by the hormones secretin and cholecystokinin.
#9 Ham sandwich digestion
salivary amylase in mouth begins breakdown of starch (in bread) to maltose in the mouth
pepsin breaks down protein (ham) into peptides in the stomach
pancreatic amylase (from pancreas) continues to break down starch into maltose in the intestines.
trypsin from pancreas breaks down more protein into peptides in the intestines
maltase from small intestine breaks down maltose into glucose
peptidases from small intestine break down peptides into amino acids
lipase, from the pancreas, digests fat (in meat and oils/fats) molecules after they have been emulsified by
bile and digests them into glycerol and 3 fatty acids (monoglycerides that can be packaged as
chylomicrons in the villi cells and then enter the lacteals.
Digestion ch34 Mader
#10 Good nutrition provides us with energy, essential amino acids, fatty acids and all necessary vitamins
and minerals for all body functions.
Consuming too many calories from any food source contributes to body fat, increasing a person’s risk of
obesity. Obesity is having 30% more than the ideal body weight for your height and body build. People
with type 2 diabetes can develop cardiovascular disease since they develop impaired insulin production
and insulin resistance. When you have insulin resistance, the body’s cells fail to take up glucose, even
when insulin is present. Glucose levels are high and show up in urine