Chapter 24 - The Digestive system - part 3 Flashcards
All blood leaving the absorptive surfaces of the digestive tract enter….
the hepatic portal system which flows into the liver
Bile salts break what down and what is this process called?
bile salts break lipid droplets apart. this is called emulsification
describe the structure of the gallbladder
hollow, pear-shaped muscular sack
Where is chemical digestion basically completed?
at the small intestine
What increases absorptive effectiveness in the small intestine?
movement of the mucosa (microvilli, villi, plicae circulares)
the movements of the mucosa do what to the intestinal contents?
stir and mix
name the 3 regions of the small intestine from proximal to distal
duodenum, jejunum, ileum
how is the small intestine adapted for the absorption of nutrients?
-the walls of the small intestine have folds called plicae circulares
-the tissue that covers the plicae circulares forms fingerlike projections (villi)
-The epithelial cells that cover the villi have an exposed surface covered by microvilli
-the small intestine has a very rich supply of blood vessels and lymphatic vessels which transports the nutrients that are absorbed
Does a high fat meal raise or lower the level of cholecystokinin in the blood?
raise
How would the pH of the intestinal contents be affected if the small intestine did not produce secretin?
the hormone secretin stimulates the pancreas to release fluid high in buffers to neutralize the chyme that enters the duodenum from the stomach. the pH of the intestinal contents would be lower than normal if the small intestine did not produce secretin
the digestion of which nutrient would be most impaired by damage to the exocrine pancreas?
lipids because the pancreas is the primary source of lipases
such damage would also reduce carbohydrate and protein digestion but not as much because these enzymes are produced by other digestive structures
the salivary glands produce enzymes that break down which biomolecule(s)
starch (carbohydrates)
the small intestine produces enyzmes that break down which biomolecule(s)
carbohydrates and proteins
the stomach produces enzymes that break down which biomolecule(s)
proteins
what is the shape of the large intestine
horse shoe shape
the large intestine begins at the ___ and ends at the ____
begins at the ileum and ends at the anus
the large intestine can be divided into 3 parts:
- The pouchlike cecum
- the colon (the largest portion)
- the rectum
Where in the large intestine does compaction begin?
the cecum
the cecum receives and stores materials arriving from where?
the ileum
where is the appendix attached to?
the cecum
the colon has a ___ diameter and ____ wall than the small intestine
larger diameter and thinner wall
What is the name of the pouches in the wall of the colon?
Haustra
What is the functional purpose of the Haustra?
to permit expansion and elongation
what creates haustra?
muscle tension in the teniae coli (3 longitudinal bands of smooth muscle)
Name the 4 regions of the colon
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
the sigmoid colon empties into the….
rectum
the ascending colon turns into the transverse colon at the….
right colic flexure
the transverse colon turns into the descending colon at the…
left colic flexure
the taeniae coli are just deep to the…
serosa
where does the descending colon become the sigmoid colon
at the sigmoid flexure
what forms the last 15cm of the digestive tract?
the rectum
what is the last portion of the rectum?
the anal canal
what is the exit of the anal canal?
the anus
Describe the structure of the anus
epidermis is KERATINIZED and identical to the surface of the skin
how many anal sphincters are there? name them
2
internal anal sphincter
external anal sphincter
differentiate between the internal anal sphincter and external anal sphincter
internal anal sphincter
-circular muscular layer
-involuntary control
-made up of smooth muscle
external anal sphincter
-encircles DISTAL portion of anal canal
-under voluntary control
-made up of skeletal muscle
does the large intestine contain villi?
NO
The large intestine contains a lot of which type of cell?
goblet cells
WHY does the large intestine contain so many goblet cells?
mucus provides lubrication for the fecal material
what are vitamins?
organic molecules that are important as cofactors or coenzymes in many metabolic pathways
what is important for the large intestine to be able to absorb vitamins?
microbiome
-microbes (bacteria, fungi, viruses)
Bacteria in the colon make 3 vitamins that supplement the diet:
vitamin k
vitamin b5
biotin
vitamin k is __ soluble
fat
biotin is ___ soluble
water
vitamin b5 is __ soluble
water
Why is vitamin K important?
the liver needs it to synthesize the 4 clotting factors, including prothrombin
why is biotin important?
important for glucose metabolism
why is vitamin b5 important?
required in the manufacture of steroid hormones and some neurotransmitters
bacteria convert bilirubin (organic waste) to which 2 things?
urobilinogens and stercobilinogens
what is the fate of some of the urobilinogens?
absorbed into the bloodstream and excreted through the urine
urobilinogens and stercobilinogens that remain in the colon are converted to….
urobilins and stercobilins (by exposure to oxygen)
what 2 reflexes move material into the cecum while we eat?
gastroileal and gastroenteric reflexes
why is movement from the cecum to the transverse colon very slow?
to allow hours for water absorption
what mechanism moves material along the length of the colon?
peristaltic waves
what mechanism mixes contents of the adjacent haustra
segmentation
movement from the transverse colon to the rest of the colon results from….
POWERFUL peristaltic contractions (mass movements)
what is the stimulus of these powerful peristaltic contractions?
the distension (swelling) of the stomach and duodenum
“the stimulus of powerful peristaltic contractions that produce movements from the transverse colon to the rest of the colon is stimulated by distention of the stomach and duodenum.”
THIS STIMULUS IS RELAYED OVER….
intestinal nerve plexuses
distension of the rectal wall initiates….
defecation reflex
the defecation reflex involves two ____ ____ loops which are both triggered by the stimulation of ____ receptors in the rectum
positive feedback
stretch
Identify the 4 regions of the colon
ascending colon
transverse colon
descending colon
sigmoid colon
What are some major histological differences between the large intestine and small intestine
large intestine — diameter is wider and walls are thinner and LACK VILLI. abundance of mucus cells and intestinal glands
Differentiate between haustral churching and mass movements
mass movements - occur a few times per day throughout the transverse colon and distal portions of the large intestine. Strong peristaltic contractions move material along the length of the colon
in haustral churning, segmentation movements mix the contents of the nearby haustrs
a balanced diet contains….
carbohydrates
lipids
proteins
vitamins
minerals
water
molecules that are absorbed into the bloodstream do one of 2 things:
-broken down to provide energy for ATP synthesis
-used to synthesize carbohydrates, proteins, and lipids
Digestive enzymes break molecular bonds in large organic molecules through a process called….
hydrolysis
Carbohydrases break bonds between…..
simple sugars
Proteases break bonds between….
amino acids
Lipases separate __ from __
fatty acids from glycerides
digestive enzymes are secreted by which 4 structures?
salivary glands
stomach
pancreas
tongue
does facilitated diffusion require ATP
NO
What component of food would increase the number of chylomicrons in the lacteals?
fats
the absorption of which vitamin would be impaired by the removal of the stomach?
vitamin b12.
absorption of vitamin b12 requires intrinsic factor , produced by the parietal cells of the stomach
why is it that diarrhea is potentially life threatening but constipation (infrequent defecation) is not
an individual with diarrhea loses fluid and electrolytes faster than it can be replaced. The resulting dehydration can be fatal
constipation can be uncomfortable, but it does not interfere with any life supporting processes. The few toxic waste products that should have been eliminated through the digestive system can instead move into the blood and be eliminated by the kidneys
identify general digestive system changes that occur with aging
-decreased secretory mechanisms
-decreased gastric and intestinal movement
-decreased division of epithelial cells
-loss of muscle tone
-cumulative damage becomes more apparent
-cancer rates increase
-dehydration occurs as a result of decreased osmoreceptor sensitivity
identify the functional relationships between the digestive system and other body systems
the digestive system absorbs organic substrates, vitamins, ions, and water required by cells of all other body systems
what body systems may be affected by inadequate calcium ion absorption?
skeletal, muscular, nervous, endocrine, and cardiovascular systems
