BIOS 100 DIGESTIVE EXCRETORY PART II
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What's small intestine consists off?
Since absorption is a surface-area phenomenon, the inner surface of the small intestine is covered withfinger-like projections called villi
Bile emulsifies fats. Pancreatic lipase digest what and what's it's route?
Glycerides into monoglycerides and fatty acids. These are absorbed into the lumen epithelium rebuilding triglycerides that transports to lymphatic system
Bile salts help do what?
They're amphipathic and help break large fat globules into smaller fat droplets- increasing surface area making lipase activity more effective.
Function of pancreas is:
- secretes three classes of digestive enzymes into the small intestine that help break down fats, proteins, and carbohydrates.
- secretes “buffers” that raise the pH of the acidic chyme coming from the stomach.
- Secretes Insulin which maintains a constant level of blood sugar
normal glucose levels in blood. Insulin stimulates it but maintained by pancreas.
What does liver and gallbladder do?
- Receives blood-borne nutrients from digestive tract.
- control nutrients to be stored sent to circulation
- gallbladder stores and concentrates bile, a substance produced by the liver that aids in the digestion of fats
Large intestine (colon) does what?
- holds and compacts material left over from digestion, turning it into feces.
- also returns water to general circulation and absorbs vitamins produced by resident bacteria.
what is mechanical and chemical digestion in parts of digestive system?
- Mouth – mechanical & chemical digestion
- Stomach – mechanical & chemical digestion
- Small Intestine – chemical digestion & nutrient absorption
- Large Intestine –
- compaction, water, and vitamin absorption
Glomerulus is a porous capillary bed how does filtration of blood occur (creation of the filtrate):
- –The diameter of the efferent arteriole is much less than that of the afferent arteriole, placing the blood in the glomerulus under great pressure
- –Fluid is squeezed through the porous walls of the glomerulus (fluid called filtrate)
- Podocytes help filter the blood, and protect the capillaries from bursting under the pressure created by the afferent and efferent artioles
Proximal tubule is removal of most nutrients, water, and other important chemicals from the filtrate and reconstitution of the blood. How is this happening?
- lumen wall of the epithelial cells absorb ions, nutrients, and water and transport them to the blood vessels nearby.
- –A Na+/K+ ATPase located on the basolateral membrane of the epithelial cell (the side of the cell opposite the lumen) actively pump Na+ out of the cell into the blood. This sets up a strong concentration gradient in the cell
How does further removal of water from filtrate of the loop of Henle occur:
- The descending limb of the loop is highly permeable to water but almost completely impermeable to solutes
- The lower portion of the ascending branch of the loop of Henle, however, is highly permeable to Na+ and Cl-, moderately permeable to urea, and almost completely impermeable to water.
- Asthe filtrate continues up the thick portion of the loop of Henle, Na+ and Cl-are actively pumped out of the filtrate into the surrounding medium.
How does further removal of water from filtrate of the loop of Henle occur: Creationof an Osmotic Gradient in the Loop of Henle
water and solutes that flowed into the medulla can be reabsorbed by the vasa recta – a network of capillaries that surround the loop of Henle and reabsorb water and solutes filtered from the blood.
Three steps in urine formation, filtration, reabsorption, and establishment of an osmotic gradient, result in a fluid that is slightly hypotonic to blood.
- Electrolytes and water are always absorbed by the distal tubule
- If the Na+ levels in the blood are low, the hormone aldosterone is released.
- This leads to reabsorption of Na+ and Cl- in the distal tubule.
ADH(antidiuretic hormone)is released if:
- a person is dehydrated. This causes aquaporin channels to be inserted in the membrane of the collecting duct so that large quantities of water can be reabsorbed.
- ADH Present - Collecting Duct is permeable to water and a small volume of urine is produced
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