lower GIT with accessory organs and structures Flashcards
(85 cards)
1
Q
describe the small intestine (6)
A
- primary site of digestion and absorption
- secretes mucus, enzymes, and hormones (cholecystokinin, secretin)
- has structures that increase its SA for absorption
- longer and narrower than the LI
- 3 sections (duodenum, jejunum, ilium)
- moves ingesta via peristalsis AND segmentation
2
Q
what does cholecystokinin affect? (4)
A
- stimulates intestinal mobility
- stimulates pancreatic enzyme production
- stimulates contraction of the gallbladder
- inhibits gastric emptying
3
Q
what does secretin do?
A
- decreases acid
- increases bicarbonate production in the pancreas and biliary ducts
- helps neutralize the pH of the chyme
4
Q
what stimulates the release of cholecystokinin and secretin in the small intestine?
A
the presence of high concentrations of amino acids or fatty acids in the chyme
5
Q
where is mucus in the SI secreted from?
A
the mucus is secreted from goblet cells
6
Q
what are the 3 specialized structures in the SI that increase its SA?
A
- circular folds
- intestinal villi
- microvilli
7
Q
describe the circular folds of the SI
A
- help increase SA
- are deep, mucosal folds
8
Q
describe the intestinal villi of the SI
A
- are long slender projections
- there is a blood and a lymph vessel in the center of each villus
- absorb nutrients through simple columnar epithelial cells
- villi cells are constantly sloughing off and being renewed
- diseases like parvo attach these cells which reduces the ability to digest and absorb nutrients
9
Q
How does the villi of the SI absorb nutrients?
A
through simple columnar epithelial cells
10
Q
describe microvilli
A
- are found on the columnar epithelial cells
- the layer where microvilli are found is called the brush border
- helps with digestion and absorption of nutrients, vitamins, and minerals
11
Q
describe the brush border
A
- the layer where microvilli are located
- the cells have many carrier molecules and digestive enzymes in their membranes
12
Q
describe the duodenum
A
- 1st section of the SI
- represents 5% of the length of the SI
- receives secretions from the liver and the pancreas
- produces digestive enzymes
13
Q
where does the duodenum receive secretions from?
A
- liver
- pancreas
14
Q
what digestive enzymes are produced in the duodenum? (3)
A
- protease (breaks down proteins)
- Amylase (breaks down carbs)
- lipase (breaks down fat)
15
Q
describe the jejunum
A
- 2nd section of the SI
- is 90% of the SI
- absorption and mixing (via segmentation)
16
Q
describe the ilium
A
- 3rd section of the SI
- represents 5% of the length of the SI
- protection (highest concentration of Peyer’s patches [lymphoid tissues])
17
Q
does the LI secrete any enzymes?
A
NO
18
Q
what are the sections of the LI?
A
- cecum
- colon (ascending, transverse, and descending)
- rectum
- anus
19
Q
does the LI have any folds or villi?
A
no
20
Q
where is the primary site of water reabsorption?
A
LI
21
Q
describe the cecum
A
- is found at the ileocecocolic junction
- is a blind-ended sac/patch
- is well-developed in all herbivores and is more developed in animals that do not ruminate
- the site of fermentation for non-ruminant herbivores (microbes break cellulose and other non-digested plant structures)
- rabbits and horses have large sacculated ceca
- absorbs volatile fatty acids
- protects (has lymphoid tissue in the walls which helps with immunity)
22
Q
what are the functions of the cecum?
A
- bacterial fermentation (microbes/bacteria breakdown cellulose and other non-digested plant structures)
- absorption of volatile fatty acids (VFAs)
- protection (lymphoid tissue in the walls wich helps with immunity)
23
Q
describe the ascending colon
A
- is from the junction with the ileum and/or cecum
- along the RIGHT side of the body
- extends cranially
24
Q
describe the transverse colon.
A
- from right to left side of the abdomen
25
describe the descending colon
- from the transverse colon to where the sigmoid curve joins the cranial rectum
- extends mostly along the left side of the body wall then enters the pelvic canal
26
describe the colon (6)
- larger lumen than the SI
- secretes mucus (large number of goblet cells, helps lubricate the lining)
-production/absorption of vitamin B and K
- mineral absorption
- the main site of fluid and electrolyte reabsorption
- propels waste towards the rectum (by segmentation and mass movement)
27
describe the rectum (4)
- the end portion of the LI
- located in the pelvic cavity
- has stretch receptors to initiate defecation reflex (contraction) when fecal matter is present which causes the contraction of the rectum and the colon
- secrets more mucus for lubrication
28
describe the anus
- terminal end of the GIT
- the exterior opening
- has 2 sphincter muscles that control defecation
- the internal sphincter is involuntary
- the external sphincter is voluntary
- the sphincters relax with defecation
29
describe the peritoneum
- is a continuous thin layer of flattened - cubed shaped cells supported by a thin connective tissue membrane
- produces a small amount of serous (watery) fluid
- supports the abdominal organs
- 2 types (parietal and visceral peritoneum)
30
describe parietal peritoneum
- the peritoneum that lines the abdominal cavity
31
describe the visceral peritoneum
the lining reflected on the visceral organs
32
describe omentum
- 2 types greater and lesser omentum
- folds of peritoneal tissue that extend from the greater or lesser curvatures of the stomach
- aka natures bandaid
- attaches to abdominal organs
- surrounds the SI and LI and a sling-like fashion
33
describe the greater omentum
- attaches to the greater curvature of the stomach, the spleen, and the coon
- extends to the ventro-lateral surface of the abdomen
- surrounds the SI and LI in a sling like fashion
34
describe the lesser omentum
- attaches at the lesser curvature of the stomach and duodenum
- extends up to the liver
35
describe mesentery
- a double fold of peritoneum
- supports the intestines
- contains blood vessels, lymphatic vessels, and lymphatic tissues
- named according to what it supports (mesoduodenum, mesojejunum, etc)
36
describe the ligaments of the peritoneum
- fold of thicker peritoneum other than mesentery or omentum
- connects organs to each other or to the parietal peritoneum
- eg, gastro-splenic ligament, broad ligament
37
describe the liver
- largest gland in the body
- located immediately caudal to the diaphragm, on the right side (especially in ruminants)
- reddish brown in color
- lobed (number carries with species)
- receives blood via 2 routes but only 1 exit vein
- there are 3 liver ligaments (coronary, falciform, and round ligament)
- 2 types of surfaces (parietal, visceral)
- have a capsule (connective tissue covering)
38
what is the largest gland in the body?
the liver
39
how many liver lobes do cats and dogs have?
6
- L and R medial lobes
- L and R lateral lobes
- the central lobe is the caudal lobe
- on the right side of the caudal lobe is the caudate lobe
40
what are the 3 liver ligaments?
- coronary ligament
- falciform ligament
- round ligament
41
describe the coronary liver ligament (location)
- very dorsal
42
describe the falciform liver ligament
- thin
- broad membrane
43
describe the round liver ligament
- ventral
- thickened portion of the falciform ligament
44
describe the parietal surface of the liver
- is one of 2 surface types of the liver
- convex shape
- faces cranio-dorsal, towards the diaphragm
45
describe the visceral surface of the liver
- is one of 2 surface types of the liver
- concave shape
- faces caudo-ventrally
46
what vessels enter the liver?
- hepatic artery (oxygenated blood)
- portal vein (nutrient-rich from intestines, stomach, spleen, and pancreas)
47
what vessel exits the liver?
- the hepatic vein
48
major liver functions (7)
- production and secretion of bile salts/ bile
- filter: metabolizes and excretes toxic substances (detoxification)
- digestion and absorption of nutrients
- process and regulate nutrient absorption
- vital in hemostasis (produces most plasma proteins and coagulation factors)
- can synthesize amino acids, and convert lipids to glucose in times of starvation
- metabolizes some minerals
49
how does the liver process and regulate nutrient absorption
- glycolysis, glycogen storage, glycogenolysis, glyconeogenisis
- breakdown of uric acid and formation of urea
- de-saturation of fatty acids
50
describe liver filtration
- phagocytic macrophages called KUPFFER cells line the hepatic sinusoids and function in the activation of T-lymphocytes
- they filter minerals absorbed from the GIT before they reach synthetic circulation
- removes toxins/poisons, worn-out RBCs, bacteria, and other infectious agents
51
describe the biliary system
- in the liver
- begins as small canaliculi between cords of cells in each liver lobule
- they unite with canaliculi from other lobules to form interlobular ducts
- the interlobular ducts joint to form hepatic ducts
52
what structures are external to the liver?(4)
- hepatic ducts (L and R)
- gall bladder
- cystic duct
- common hepatic/bile duct
53
describe liver and plasma proteins
- the liver produces several major blood plasma proteins and coagulation factors
- help regulate fluid balance and coagulation
*eg if albumin decreases as a result of liver failure, fluid leaks out of capillaries and into tissues and cavities (edema, ascites, etc)
*lack of clotting factor can cause even the tiniest injury to be fatal
54
describe bile
- greenish
- alkaline
- viscous
- liver secretion
55
what is bile composed of? (6)
- bile salts
- water
- phospholipids
- cholesterol
- bile pigments
- lecithans
56
what is bile necessary for?
- lipid digestion
- because it has hydrophilic and hydrophobic aspects to emulsify fats
57
what does bile help transport?
- waste products (like bilirubin from the breakdown of RBCs)
58
how does bile get to the duodenum
1. hepatic cells secrete bile salts into the canaliculi
2. travels through the bile ducts
3. enters the duodenum via the common bile duct
4. OR is stored in the gall bladder
59
cholelithiasis
gall stone
60
describe the gallbladder
- stores bile
- releases bile into the duodenum when fats are present
- gallbladder contraction is stimulated by cholecystokinin
- is not necessary for survival
61
which species don't have a gallbladder?
- horse
- deer
- rat
- tapir
- elephant
- rhinoceros
(because they don't eat much fat and they're grazers)
62
describe the pancreas
- located in the right cranial quadrant of the abdominal cavity, along the inner border of the duodenal loop
- is an elongated, flattened structure, a rough, glandular look, cream to brown color
- in some species, it shares the common bile duct with the gall bladder (horse, sheep, humans)
- both exocrine and endocrine functions
63
describe the pancreatic duct in different species
- separate: pig, cow
- joined with the common bile duct: horse, sheep, humans
- Both, dogs have 2 ducts, one shares with the common bile duct
64
what are the pancreatic endocrine functions?
- secrete substances released into the bloodstream, travels systemically
- the effect is far from the source
- releases important enzymes: insulin, glucagon, pancreatic polypeptide, somatostatin
65
what are the pancreatic exocrine functions
- it secretes substances
- released via ducts/ glandular cells directly to an area for local effect (usually onto an epithelial surface)
- excretes digestive enzymes and their precursors into the pancreatic duct
- releases sodium bicarb ions making the pancreatic juice less acidic, neutralizing the stomach acid
- releases 3 types of enzymes (amylase, protease, lipase )
66
failure to produce enough insulin leads to what?
diabetes Mellitus
67
what can pancreatic failure result in? (2)
- diabetes mellitus
- maldigestion
68
enzymes of digestion
- chemical substances responsible for the enzymatic breakdown of foodstuff into a more simple form for absorption
69
breakdown of carbohydrates
carbohydrates
polysaccharides
disaccharides
monosaccharides
70
breakdown of proteins
proteins
peptides
amino acids
71
breakdown of fats
fats
fatty acids and glycerol
72
describe chyme
- the product of mechanical and chemical breakdown of food on the stomach (food is mixed with secretions until it is reduced to a liquid)
- homogenous
- creamy/gruel-like
73
describe gastric juices
- mixture of HCl, mucus, pepsinogen, chymosin, gastric lipase, and gastrin
74
describe pepsinogen
- an enzyme secreted by the stomach
- reacts with the acid to produce pepsinogen
- pepsin is responsible for initiating the breakdown of protein
75
describe chymosin
- secreted by the stomach
- formerly called Rennin
- milk curdling enzyme (is present in young to coagulate milk)
- facilitates milk digestion
76
describe gastric lipase
- an enzyme secreted by the stomach
- breacks down fats into fatty acids and glycerol
- generally produced in the pylorus
77
describe gastrin
- secreted near the pylorus
-causes:
* increased peristaltic activity in the digestive tract
* increased hydrochloric secretion
* relaxation of the pyloric sphincter
* constriction of the esophageal sphincter
78
what is secreted in the intestines (8)
- cholecystokinin
- secretin
- villikinin
- trypsin
- maltase, sucrose, and lactase
- nuclease
79
describe cholecystokinin
- secreted from the duodenum
- release is stimulated by the presence of fat
- causes decreased stomach motility
- decreases stomach secretion
- increased release of pancreatic secretions
- causes contraction of the gall bladder and relaxation of the gall bladder sphincter
80
describe secretin
- duodenal secretion
- stimulated by increased acidity in the intestinal contents
- causes a decrease in the stomach motility and secretions
- increases the secretion of bicarbonate from the pancreas and liver
- increases bile secretion
81
describe villikin
- duodenal secretion
- stimulated by the presence of chyme in the upper intestine
- causes increased movement of the villi
- aids in absorption
82
describe trypsin
- intestinal secretion
- breaks down dipeptides
83
describe maltase, sucrose, and lactase
- intestinal secretion
- breaks down disaccharides
84
describe nuclease
- intestinal secretin
- helps digest/breakdown/ act on nucleic acids
85
describe elastase
- pancreatic secretion
- acts on elastin
