Body Systems Bio 20 AP Digestion

Works to chemically digest food, absorb nutrients, and transport undigested waste to the large intestine via peristalsis.

• - 7m long, 2.5 cm in diameter
• - pH of 8

• - 3 segments
•         - Duodenum (Start)
•         - Jejunum (Middle)
•         - Ileum (End)
• - Structural unit of the S.I. is the villus
•         - Each villi is covered in microvilli
•         - It's full of blood vessels (capillary network) that take in the absorbed amino acids and glucose
•         - There is also a lacteal, which is a small vessel within the villi that absorbs the fatty acids into the lymphatic system

It is more energy efficient because it takes less energy to move something that has a small volumn.

They work to increase the chances that a nutrient will be absorbed by increasing the surface area inside of the S.I. The villi are one cell thick because it is easier for nutrients to move through one cell than many.

Its important to have a large surface area to volume ratio. This is because a large surface area increases the chances that something will bump into the it, which will increase the cell's survival rate.

The larger the surface area is to the cell's volume, the easier it is to survive because while some nutrients can be used to sustain the cell, the rest can be stored so for emergencies. This is an option that is available to smaller volume cells, in comparison to large volume cells, where all the nutrients are needed to sustain the cell, so they don't have emergency reserves.

Absorb amino acids and glucose via active transport (ATP and transport proteins) in the small intestine.

Glucose and AA are too big to diffuse over the cell membrane, so transport proteins are needed. These proteins are powered by ATP. Active transport is also used because you want all the nutrients, not just half and half.

Absorbs lipids via diffusion in the small intestine.

• Function: Secretes enzymes and chemicals
• Secretes:
• - Prosecretin --> Secretin (active form)
•          - Secretin produces bicarbonate ions (HCO3-)
• - Trypsin (Trypsinogen)
• - Erepsin 
• - Amylase
• - Lipase

Secretin is the active form of prosecretin. It is produced in the pancreas and it produces bicarbonate ions (HCO3-).

Produced in the pancreas by secretin and it functions in the small intestine. It is basic, so it neutralises the acidic chyme coming from the stomach. It essentially acts as TUMS. It also deactivates pepsin into pepsinogen. It does this so that the pepsin doesn't digest the small intestine.

It is a hardcore protein enzyme that breaks proteins into polypeptides. Pepsin is the active form and pepsinogen in the inactive form. It is activated by hydrochloric acid in the stomach and deactivated by bicarbonate ions in the small intestine. It is made in the stomach and functions in the stomach.

It's a protein enzyme that breaks polypeptides into peptides. It's gentler than pepsin, so it won't digest the small intestine. Its active form is trypsin and the inactive form is trypsinogen. It is activated by Enterokinase. It is made in the pancreas and it functions in the small intestine. 

It breaks peptides into amino acids. It is made in the pancreas and it functions in the small intestine.

It digests carbs (di, poly). It is first made in the salivary glands and functions in the mouth. To later assist in digestion, it is again made in the pancreas and functions in the small intestine.

It digests lipids. It is made in the pancreas and functions in the small intestine.

The first segment of the small intestine. The chyme from the stomach flows into here. The bile salts needed for digestion arrive here from the gall bladder. The enzymes and HCO3- from the pancreas arrive here too.

inactive

They are named after their substrate, with the ending changing into "ase".

• - Produces bile salts (chemical)
• - detoxifies the blood by filtering/removing toxins
• - Stores glycogen and Vitamin A, D, & B12
• - Recycles old RBC

Stores bile salts made by the liver until it is time to release them to aid in lipid digestion. When there are fats in the duodenum, cholecystokinin (CCK) sends a chemical message from the duodenum to make the gall bladder release the bile salts into the S.I.

A chemical used during lipid digestion to physically digest (cut) fats in the duodenum. It's made in the liver and stored in the gallbladder and released when a chemical message is sent by cholecystokinin (CCK).

Polysaccharides are chemically digested by the enzyme amylase, and broken down into disaccharides and then monosaccharides (glucose) via hydrolysis. These glucose molecules are then absorbed by the villi in the S.I. into the blood stream via active transport (transport proteins powered by ATP).

A fat, like a triglyceride, is physically digested (emulsified) by bile salts. The smaller triglyceride chunks are then chemically digested into fatty acids and glycerol units via hydrolysis by the enzyme lipase. The fatty acids and glycerol is absorbed into the villi of the S.I. via diffusion. These lipid monomers are then reassembled into triglycerides and attached to proteins, which then make their way into the lacteal of the villi and then the lymph vessal.

Large proteins are broken into polypeptides in the stomach by pepsin via hydrolysis. Once the chyme has moved into the S.I. the pepsin is then deactivated by HCO3-. The polypeptides are then broken into peptides by trypsin, which is activated by enterokinase in the S.I. In the final stage, erepsin breaks the peptides into amino acids. The amino acids are then absorbed into the villi and then bloodstream via active transport (transport proteins are powered by ATP).

Bile salts and cholesterol form large crystals that block the bile duct. This keeps bile salts from entering the duodenum and prevents fats from being digested.

The yellowing of the skin. It occurs because bile salts produced in the liver can't get to the gall bladder because the bile duct is blocked by a gallstone. So, the bile salts diffuse into the bloodstream connected to the liver because the concentration of bile salts in the bloodstream is low compared to the liver. The bile salts then break down the RBC is the bloodstream, which causes the skin to look yellow instead of reddish.

Damaged liver tissue gets replaced by non-functioning fat and connective tissue (cartilage), which leads to a further lack of blood filteration. It is caused by drug overloading.

• - Mostly absorbs water
• - Can absorb some salts (any ionic compound)
• - Can absorb any nutrients missed by the S.I.
• - Stores non-digestible waste
• - Houses E.Coli, which eat poop and synthesize vitamin B and K

• - 1.5m x 7.6cm tube
• - Has villi with microvilli that increase surface area, which aids in absorbing water and any leftover nutrients

• - Presence of food in the mouth/stomach, seeing/smelling, swallowing, stimulates gastric juice production
• - Food in the stomach/smell/sight/taste wakes up gastrin, which wakes parietal cells (cells immediately on the inside of the stomach), which produce HCl
• - Fats in the S.I. wake enterogastrone, which slows peristaltic movement

• - Esophagus
• - Bile Duct
• - Stomach
• - Pancreas
• - Small Intestine
• - Large Intestine
• - Rectum
• - Appendix
• - Duodenum
• - Gall Bladder
• - Liver 
• - Salivary Glands
• - The types of teeth
• - Epiglottis
• -Villi and Microvilli
• - Lower Esophageal 
• - Pyloric