Human physiology digestion

what is mechanical digestion

physical breakdown of food into smaller pieces, chewing and churning

what is chemical digestion

breakdown of food ising enxymes and acids into smaller molecules that can be absorbed

What are the 6 digestive processes

ingestion, propulsion, mechanical digestion, chemical digestion, absorption, defecation

What is the enteric nervous system

“brain of the gut” that controls digestion independently of the CNS

What are long reflexes

reflexes involving CNS that regulate digestion

what are short reflexes

Local reflexes within the GI tract controlled by ENS only

What stimulates digestive activity

streatching of organs, pH changes, nutrients in food, and hormones (CCK, secretin, gastrin)

what happenes in the mouth

mechanical digestion (chewing) + salivary amylase begins carbohydrate digestion

What is the role of saliva

moistens food, contains enzymes (amylase), and helps form bolus for swallowing

what happens in the esophagus?

deglutition (swallowing) and peristalis move food to the stomach

what do chief cells secrete

pepsinogen (inactive enzyme form)

why is pepsinogen inactive

prevents the stomach from digesting itself

what activates pepsinogen

HCI converts it into active pepsin

What doe parietal cells secrete

hydrochloric acid (HCL) and intrinsic factor

what does HCL do?

Activates pepsin, kills bacteria, denatures proteins

what happens in the stomach

mechanical mixing + protein digestion + acidic breakdown of food into chyme

what froms the mucosal barrier in the stomach

mucus layer, tight junctions between cells, bicarbonate secretion

what can cause stomach ulcers?

pylori infection, NSAIDs, excess acid, weakened mucosal barrier

why is the pancreas both endocrine and exocrine

Endocrine = releases hormones into blood (insulin, glucagon).
Exocrine = releases digestive enzymes into ducts.

what stimulates CCK release

fat and protein in the small intestine

what stimulates secretin release

acid (low pH) in the small intestine

where do CCK and secretin come from

small intestine (Duodenum)

what does CCK do

stimulates pancreatic enzyme release and gallbladder contraction (bile release)

what does secretin do

stimulates bicarbonate release from pancreas to neutralize acid

what cells produce insulin

Beta cells (B cells)

what cells produce glucagon

Alpha cells (a cells)

what does insulin do

lowers blood glucose bby promoting uptake into cells and storage

what does glucagon do

raises blood glucose by stimulating glycogen breakdown

what is diabetes mellitus

a condition where blood glucose regulation is impaired (lack of insulin or resistance)

how can diabetes lead to acidosis

fat breakdown → ketone bodies → acidic blood (ketoacidosis)

what is a GLP-! agonist

drug that mimics incretin hormone GLP-1

what is emulsificaiton

breaking far into small droplets to increase surface area for digestion

what does bile do in emulsification

breaks fat into tiny droplets (no enzyme needed)

what do lacteals do

absorb fats into lymphatic system

what is the job of the small intestine

main site of digestion and nutrient absorption

how does the small intestine increase absorption

villli, microvilli, and circular folds increase surface area

what is mass movement

strong paristaltic wave that moves feces through colonwhy

is bacterial flora inportant in the large intestine?

produces vitamins (especially vitamin K and B), helps digestion

why must you eat low fat after gallbladder removal

no bile storage → fat digestion is less efficient, so large fat meals are harder to process