Digestion

Question 1

digestion process

Answer 1

mouth
1. Entry via mouth
2. Mastication breaks food into smaller pieces
3. Saliva softens, lubricates, dissolves food particles
Pharynx
1. Bolus is moved back into pharynx by tongue
2. Bolus is in pharynx then swallowed into esophagus
3. Epiglottis closes off trachea during swallowing to prevent food from entering windpipe
Esophagus
1. Upper esophageal sphincter up to receive bolus then closes behind
2. Bolus travels through to lower esophagus initiating and continuing peristalsis
3. Bolus goes through lower esophageal sphincter and enters stomach
Stomach
1. Continues mechanical digestion by contracting and churning to mix food with digestive juices for several hours
o Digestive secretions: HCL, enzymes pepsin & lipase, mucus for lubrication and protection, intrinsic factor for B12 absorption, gastrin
o HCl activates pepsin which enhances the absorption of minerals and & breaks down connective tissue of meat
2. Bolus of food becomes chyme, a semiliquid substance
3. Chyme is released from stomach into the small intestine via the Pyloric Sphincter
Small intestine
1. chyme enters from pyloric sphincter and goes through duodenum to cecum where segmentation, pendular movement which enhances nutrient absorption, and peristalsis occurs to digest the food
2. nutrient uptake, absorbs water, bile acids recycling
Large intestine = colon
- Intestinal matter passes through colon in 12 to 24 hours depending on age, health, diet, fiber intake– Bacteria in colon produce vitamin K and biotin and break down fiber and undigested carbohydrates, producing methane, carbon dioxide, hydrogen gas, and other compounds
- Stool, or feces, is stored in the rectum
Anal canal
- is connected to the rectum and controlled by two sphincters: internal and external
Final stage of defecation is under voluntary control

Question 2

organs involved with digestion

Answer 2

• Main organs:
  1. Mouth
  2. Pharynx
  3. Esophagus
  4. Stomach
  5. Small intestine
  6. Large intestine
  7. Anal canal
• Accessory organs: teeth, tongue, salivary glands, liver, gallbladder, pancreas

Question 3

enzymes
- function
- primary action
- source of origin

Answer 3

function: speed up chemical reactions to break apart food
- secreted by salivary glands, stomach, pancreas, small intestine
- enzymes from pancreas are responsible for a large portion of digested nutrients
o amylase: digests carbs into glucose
o lipase: digests fats into fatty acids
o trypsin, chymotrypsin, carboxypeptidase (proteases): digest proteins into amino acids

Question 4

Hormones and digestion
- function
- primary action
- source of origin

Answer 4

• hormones control digestive secretions, regulate enzymes & cellular activity
• gastrin: stimulates stomach to release HCl and gastric lipase
• ghrelin: stimulates hunger
• secretin: causes pancreas to release bicarbonate
• cholecystokinin (CCK): stimulates pancreas to secrete digestive enzymes, controls pace of digestion
• paracrine digestive hormones: secreted by enteroendocrine cells but travel to nearby tissue where they carry out acts for digestion like somatostatin and histamine

Question 5

bile and digestion
- function
- primary action
- source of origin

Answer 5

• made in liver and stored in gallbladder
• helps digest fat by breaking down large fat globules into smaller fat droplets
• can be reused by recycling through liver from large intestine through enterohepatic circulation (entero = liver, hepatic = liver)

Question 6

absorption

Answer 6

• Absorption of nutrients through the walls of the intestines go into circulatory or lymphatic system
• Sent to liver for processing before delivering to the body’s cells
• 3 methods of absorption in small intestine: passive diffusion, facilitated diffusion, active transport (against conc gradient)
• Liver’s role in absorption: processes materials absorbed by small intestine and create the necessary chemicals

Question 7

how does circulatory and lymphatic system transport absorbed nutrients

Answer 7

• Circulatory system: distributes water soluble nutrients through blood
• Lymphatic system: distributes fat soluble nutrients through lymph vessels
• Blood and lymph are fluids that circulate throughout the body. They both distribute nutrients to cells and blood also picks up waste products for excretion. The lymph eventually connects with the blood near the heart (subclavian veins).
• Nutrients travel to blood capillaries and lacteal within the villus. Water soluble nutrients are displayed in the bloodstream and fat soluble nutrients are displayed in the lacteal.
• Fat digestion, must pass through the lymphatic system before they enter the bloodstream because they are too large to enter the bloodstream directly. Lymph also transports fat soluble vitamins from intestinal tract to blood
• Chyle made of lymph and tiny fat droplets is the clear fluid that carries fats and proteins, helps fight germs, and keeps the body’s fluid levels normal

Question 8

basics of excretory system

Answer 8

• Removes excess and waste products to maintain homeostasis
• Most products are broken down components of metabolism which leave in the form of sweat, urine, feces
• Protein break down results in nitrogenous waste like urea
• Kidneys make nitrogenous waste concentrated into urine for excretion