MCAT BIO CH. 10 PART 2 Flashcards
What are the lower segments of the small intestine?
Jejunum and ileum
Substances not absorbed in the duodenum must be absorbed where?
Jejunum and Ileum
In what portion of the intestine is vitamin B12 absorbed?
Only in the ileum
What is the iléocaecal valve?
Separates the ileum from the cecum, which is the first part of the large intestine
What is the colon?
Large intestine
What is the role of the colon?
Absorb water and minerals, form and sore feces until defecation
What is the first part of the colon?
Cecum
What is the structure of the appendix?
Finger-like appendage of the cecum
What is the appendix primarily composed of?
Lymphatic tissue
What is the last portion of the colon?
Rectum
What is defecation controlled by?
Anal sphincter
What is the different between the internal and external portion of the anal sphincter?
Internal: Smooth muscle under autonomic control
External: Skeletal muscle under voluntary control
What is the important of colonic bacteria?
- Helps keep dangerous bacteria from proliferating due to competition
- Supply us with vitamin K
What does a GI accessory organ mean?
Those that play a role in digestion but are not actually part of the alimentary canal
What are the GI accessory organs?
Pancreas, liver, gallbladder and salivary glands
What is the purpose of pancreatic amylase?
Hydrolyzes polysaccharides to disaccharides
What is the purpose of pancreatic lipase?
Hydrolyzes triglycerides at the surface of a micelle
What is the purpose of nucleases from exocrine pancreas?
Hydrolyze dietary DNA and RNA
What is the purpose of pancreatic proteases?
Hydrolyzing polypeptides to di and tripeptides
How are pancreatic proteases secreted?
Secreted in their inactive zymogen forms
What is the role of trypsinogen in regards to exocrine pancreas?
A zymogen that gets converted into active form trypsin by enterokinase
What enzymes are activated by trypsin?
- Chymotrypsinogen
- Procarboxypeptidase
- Procollagenase
What does CCK secretion causes the pancreas to do?
Secrete enzymes
What does the secretion hormone cause the pancreas to do?
Secrete water and bicarbonate
What is the effect of parasympathetic and sympathetic nervous system on pancreatic secretion?
Para: Increases secretion
Symp: Reduces it
Where are the endocrine pancreas located in the pancreas?
Islets of Langerhans
What are the three types of cells in the islets of langerhans?
- Alpha cells
- Beta cells
- Omega cells
What do the alpha cells of the islets of langerhans?
Secrete glucagon in response to ow blood sugar
What is the function of glucagon?
Mobilize stored fuels by stimulating the liver to hydrolyze glycogen and release; stimulate adipocytes to release fats
What do the beta cells of the islets of langerhans?
Secrete insulin in response to elevated blood sugar
What is the function of insulin?
Stimulates removal of glucose from the blood for storage as glycogen and fat
What do the omega cells of the islets of langerhans?
Secrete somatostatin
What is the function of somatostatin?
Inhibits many digestive processes
What is the problem with excess glucose?
Destroys many physiological systems at the cellular level, including neurons, blood vessels and kidneys
What are the three hormones that can raise blood glucose level?
- Glucagon 2. Epinephrine 3. Cortisol
Why is it less easy to lower blood glucose?
Since low blood glucose levels are immediately fatal
What is the exocrine secretory activity of the liver?
Secretes bile
What are the principle ingredient of bile?
Bile acids, cholesterol and bilirubin
What is bilirubin?
RBC breakdown
What happens to the bile made in the liver?
- Secreted into the duodenum
2. Stored for later use in the gallbladder
What happens to the bile when it is stored in the gallbladder?
Released when a fatty meal is eaten
What is a gallstone?
Large crystal formed from bile made with ingredients in incorrect proportions
The gallbladder has secretion activity. T/F
False: no secretory activity
Bile released from the gallbladder is dictated by what?
Nervous system and endocrine system
From where does the liver receive blood?
- Hepatic arteries - oxygenated blood
2. Hepatic portal vein - venous blood drawing the stomach and intestines
What do hepatocytes do when the logo percolates through the liver?
Monitor the blood and makes changes to the body’s physiology based on what is and not present
What can store glucose as glycogen and break it down when glucose is needed?
Liver and skeletal muscle
Which organ is the only that can release glucose into the bloodstream?
Liver
Why can only the liver release glucose into the bloodstream?
Product of glycogen breakdown is glucose-6-phosphate and only the liver contains the enzyme to dephosphorylate it
Which organ monitors waste products from protein catabolism?
Liver
How can the liver regulate ammonia?
Converted into urea
Which organ assists with lipid metabolism?
Liver
What are chylomicrons?
Molecules that transport lipid into the lymphatic system
What is the result of chylomicrons breakdown?
Triglyceride, glycerol and cholestrol-rich chylomicron remnants
What happens to chylomicron remnants?
Taken up by hepatocytes, combined with proteins to make lipoproteins
Why does people with liver problems often have troubles with sealing wounds?
Important plasma proteins are made in the liver and secreted in the plasma
What is different in the smooth ER of hepatocytes?
Contains enzymes pathways that break down drugs and toxins
What happens based on hormonal control when the stomach is empty?
Gastric cells produce the hormone gherlin to stimulate appetite
What happens based on hormonal control when the stomach is full?
The jejunum produces peptide YY to reduce appetite
What is the purpose of the hormone leptin?
An appetite suppressant that acts as an adipostat
What is an adipostat? Which hormone controls like that?
Maintaining stable lipid content in adipose tissue - leptin
Where is hormone leptin produced?
White adipose tissue
When is leptin secreted?
In repos-one to increased triglyceride levels and works to suppress appetite
The effects of hormonal control of appetite Is primary mediated by…?
The arcuate nucleus of the hypothalamus
Disruption of leptin signaling in animal causes what?
Obesity
What are the categories of vitamins?
Fat soluble and water soluble
What do fat soluble vitamins require?
Bile acids for solubilization and absorption
Excess fat soluble vitamins are stored where?
In adipose tissue
Excess water soluble vitamins are excreted where?
In urine by the kidneys
What are the 4 fat soluble vitamins?
A, D, E and K
What are the water soluble vitamins?
B 1, 2, 3, 6, 12, C, biotin and folate
What is the purpose of vitamin A?
Visual pigment
What is the purpose of vitamin D?
Control calcium deposition
What is the purpose of vitamin E?
Prevents oxidation of unsaturated fats
What is the purpose of vitamin K?
Formation of blood coagulation factors
What is the purpose of vitamin B1?
Thiamine - enzymatic decarboxylations
What is the purpose of vitamin B2?
Riboflavin - Made into FAD, electron transporter
What is the purpose of vitamin B3?
Niacin - Made into NAD electron transporter
What is the purpose of vitamin B6?
Pyridoxine - coenzyme involved in protein and amino acid metabolism
What is the purpose of vitamin B12?
Cobalamin - coenzyme involved in the reduction of nucleotides to deoxynucleotides
What is the purpose of vitamin C?
Ascorbic acid - collagen formation; deficiency = scurvy
What is the purpose of biotin?
Prosthetic group essential for transport of CO2 groups
What is the purpose of folate ?
Enzyme cofactor - used in transport of methylene groups, synthesis of purines and thymine, needed for normal fetal nervous system
