Chapter 8: Digestive And Excretory Systems Flashcards
1
Q
Glucose transport protein moving glucose into enterocyte
A
- Sodium-glucose linked transporter (SGLT1): transports glucose and Na+ into enterocyte down the concentration gradient of Na+
1a. to maintain Na+ gradient, Na+ is pumped back out via Na+/K+ pump - Carbs are then absorbed into blood and carried by hepatic portal vein to liver
2
Q
Protein absorption
A
- Di/tripeptides are absorbed into enterocyte where they are hydrolyzed into amino acids and absorbed into blood via facilitated or active transport
3
Q
Lipid absorption
A
- Dietary fat is broken down into triacylglyceride which are broken down into monoglycerides and fatty acids which are then shuttled to brush border via micelles
- Then small fatty acids diffuse in while larger ones get shuttled in
- Once in enterocyte, fatty acids and monoglycerides are converted into TGs in SER and form a chylomicron
- Chylomicron sticks to capillaries where lipoprotein lipase hydrolyzes the TGs that can diffuse into muscle and adipose to be stored
4
Q
GI tract: mouth / esophagus
A
- Digestion of starch (carbs) begins here with amylase in saliva
- Chewing breaks food down to become a coleus that can be pushed into esophagus
- Bolus moves down esophagus via peristalsis (via smooth muscles)
5
Q
GI tract: Stomach
A
- Bolus moves into stomach via lower esophageal/cardiac sphincter
- Peristalsis allows mixing of bolus into becoming chyme
- Gastric pits/glands in stomach have 4 cells:
3a. Mucous cells: secrete mucin to lubricate stomach so food can pass without damage
3b. Chief/peptic cells: secrete pepsinogen that is cleaved via low pH which activates it to pepsin which can begin protein digestion
3c. Parietal/oxyntic cells: secrete HCL (activated via gastrin, Ach, histamine) to acidify the stomach (alkaline tide) and intrinsic factor that helps lumen absorb vitamin B12 for RBC production
3d. G cells: secrete gastrin which helps parietal cells secrete HCL
6
Q
GI tract: pancreas
A
- Chyme is then released from stomach through pyloric sphincter into small intestine (duodenum)
- Pancreas secretes bicarbonate to raise duodenums pH to 6 & secretes pancreatic polypeptide (via PP cells) which regulates digestive enzymes from pancreas and slows rate chyme entered duodenum
- Has acinar cells that secrete digestive enzymes:
3a. Protein digestion: trypsin, chymotrypsin and carboxypeptidase
3b. Carb digestion: pancreatic amylase
3c. Lipid digestion: pancreatic lipase, phospholipase
7
Q
GI tract: Gallbladder and bile
A
- Bile is produced in liver and stored in gallbladder which releases it via cystic duct-> common bile duct -> pancreatic duct -> duodenum
- Emulsifies fats
8
Q
GI tract: small intestine
A
- 90% of absorption happens here
- Has brush border that contains digestive enzymes which finish the job of digestion that was begun via pancreatic enzymes
- Within villi they have exocrine glands called crypts of leiberkuhn which have:
3a. Planeth cells: has lysozyme to maintain bacteria in intestine
3b. Goblet cells: secrete mucous
3c. Runners glands: secrete mucous and bicarbonate
3d. Stem cells
9
Q
GI tract: Large intestine
A
- Main functions are water and electrolyte absorption
1a. Vitamin K is made here - Made up of colon (cecum, ascending colon, transverse colon, descending colon and sigmoid colon), rectum and anal
10
Q
Enteric nervous system
A
- A network of neurons that innervate GI tract and regulate motility, secretion, blood flow etc
- Has 2 plexus
2a. Myenteric (Auerbachs) plexus: motility
2b. Submucosal (Meissner) plexus: secretion and absorption - Interacts w gut microbiota
11
Q
Enteroendocrine cells + their hormones
A
- G cells in stomach: gastrin which activates parietal cells to secrete HCL which activates chief cells pepsinogen into becoming pepsin
- I cells in duodenum: CCK increases bile secretion, pancreatic enzymes etc
- S cells in duodenum: Secretin is activated by low pH and increases water secretion to raise pH
- Ghrenlin cells secrete ghrelin: signals that we are hungry
12
Q
Liver functions
A
- Storage
1a. Blood and glucose storage
1b. Vitamin and mineral storage: A,D,E,K,B12 - Filtration
2a. Blood filtration
2b. Erythrocyte destruction
2c. Detoxification - Metabolic
3a. Carb, protein and fat metabolism
13
Q
Kidney: urine path
A
- Urine is created by kidney and emptied in renal pelvis which is emptied into ureter which carries urine to bladder which is then drained by urethra
14
Q
Functions of kidneys
A
- Filter blood and excrete waste
- Homeostasis of body fluids
- Control of blood pH
15
Q
Nephron function
A
- Functional unit of kidneys
- Processes of nephron
2a. Filtration: when blood plasma is filtered as it enters nephron
2b. Reabsorption: process where water and some solutes are returned to body from filtrate
2c. Secretion: where water and some solutes are expelled from kidney to filtrate
