Chapter 6- Human Physiology Flashcards
Name the structure of the small intestine from outward to inward.
Serosa
Longitudinal Muscle [SMOOTH MUSCLE] (Helps make it longer)
Circular Muscle [SMOOTH MUSCLE] (Helps squeeze it)
Submucosa
Mucosa
Lumen (lined with Villi)
Serosa
An outer coat = Tough/ Flexible/ Strong/ Surrounding outside (where pancreas is)
Submucosa
Tissue layer containing blood and lymph vessels.
Connective tissue betw. mucosa and muscle layer
Mucosa
The lining of the small intestine, w. epithelium that absorbs nutrients on its inner surface.
Mesentry
Hanging part of the small intestine = has the blood supply and nerve supply
What does the contraction of circular muscle behind the food do?
Constricts the gut = prevents it from being pushed back to the mouth.
What does the contraction of longitudinal muscle where the food is located do?
Moves food along the gut.
What is the main funct. of peristalsis in the intestine?
Churning of semi digested food to mix it w. enzymes and speeds up the digestion process.
Endocrine glands (in pancreas) what are they and what do they secrete?
Secretes Insulin and Glucagon (hormone) INTO THE BLOOD.
Exocrine glands (in pancreas) what are they and what do they secrete
Synthesis and secretes digestive enzymes INTO THE GUT in response to eating a meal.
What are contractions of muscles controlled by?
Enteric Nervous System
What is the name of the cell that secretes digestive enzymes?
Acinar cells
Enzymes secreted by the pancreas.
\+ Amylase \+ Lipase \+ Protease \+ Phospholipase \+ HCO3 (Hydrogen carbonate) Buffer
Why is the hydrogen carbonate an essential secretion from the pancreas?
The pH int he stomach = low cuz of the HCl
+ before it enters the intestine = needs to be made to abt pH 7 so it doesn’t corrode the cell lining of the small intestine.
Amylase digests?
Starch into Maltose
Lipase digests?
Triglycerides into:
+ Fatty acids and glycerol
+ Fatty acids and monoglycerides
Phospholipase digests?
Phospholipids into:
+ Fatty acids
+ Glycerol
+ Phosphate
Protease digests?
Proteins and Polypeptides into:
+ Shorter peptides
What form are most of the enzymes secreted by the small intestine in?
Immobilised in the plasma membrane of epithelium cells lining the intestine.
They are active there an continue to be active when epithelium cells = scraped away, off the lining and mixed w. semi digested food.
Nucleases digest? (Synthesised by small intestine)
DNA and RNA into Nucleotides
Maltase digests? (Synthesised by the small intestine)
Maltose into Glucose
Lactase digests? (Synthesised by the small intestine)
Lactose into Glucose and Galactose
Sucrase digests? (Synthesised by the small intestine)
Sucrose into Glucose and Fructose
Exopeptidase and proteases digests? (Synthesised by the small intestine)
peptides into dipeptides
Depeptidase digests? (Synthesised by the small intestine)
Dipeptides into amino acids
What does Villi do to the small intestine?
Increases the surface area of epithelium of which absorption = carried out.
Absorption
The process of taking substances into the cell and the body.
For nutrients to be absorbed into the body, what must it first be absorbed into?
The epithelium cells through the exposed part of a plasma membrane that has a surface area enlarged w. micro villi.
Once the nutrients pass into the epithelium cell from the lumen of intestine, where does it go?
Absorbed into the lacteal (part of lymphatic system)(fats) or into the blood capillaries.
What are the 4 different mechanisms that move nutrients into and out of the villus epithelium cell?
- Simple diffusion
- Facilitated diffusion
- Active transport
- Exocytosis
How are triglycerides absorbed into the body?
- They must be digested = fatty acids and monoglycerides
- 1 Monoglycerides can be absorbed into the villus epithelium cell by SIMPLE DIFFUSION
- 2 Fatty acids absorbed by FACILITATED DIFFUSION via Fatty acid transporters (protein channels)!
- Inside the epithelium cell = fatty acids and monoglycerides combine = triglyceride = can’t diffuse back into lumen.
- Triglycerides = combine w. cholesterol to form droplets = become coated in phsopholipids and proteins = LIPOPROTEIN.
- Lipoprotein = released by exocytosis through plasma membrane on inner side of villus
- Either enter lacteal OR enter blood capillaries
Why can’t glucose enter the plasma membrane by ‘simple diffusion’?
Its POLAR = its hydrophilic!
How is glucose absorbed into the body?
- Sodium-Potassium pumps (on the inwards facing parts of the plasma membrane) = PUMPS 3Na+ ions by ACTIVE TRANSPORT from cytoplasm to the interstitial spaces inside the villus and 2K+ ions the opposite way!
- Sodium-Glucose co-transporter proteins in the (micro villi) = transfer a Na+ ion and a glucose molecule together from the intestinal lumen to the cytoplasm of epithelium cells
THIS is a passive FACILITATED DIFFUSION that depends on the conc. grad of Na+ ions created by active transport. - Glucose channels allow FACILITATED DIFFUSION of glucose from cytoplasm into the interstitial spaces inside the villus then into the blood capillaries.
Pinocytic vesicles contain?
Liquid
Phagocytic vesicles contain?
Solid
What does starch digestion in the small intestine illustrate?
+ Catalysis
+ Enzyme specificity
+ Membrane permeability
Properties of arteries (2)
1) Elastic Tissues in the wall
→ elastin fibres = store energy that stretches them at peak of each pumping cycle = recoil helps propel blood down artery
2) Smooth muscles contractions in artery walls determine diameter of lumen