U23 digestive tract

Tongue

repositions food

mixes it with saliva to form a lump - BOLUS

initiate swallowing

assists in speech

Papillae

filiform - gives friction and most common. smallest

fungiform - tastebuds buds, mushroom shaped

vallate - taste buds, secretes lingual lipase, in “V“ form

foliate - taste buds, secretes lingual lipase, pleats on lateral surface

Salivary Glands

• make 1.5 L

• cleans mouth

• dissolves food

• moistens food

• protects against bacteria

Enzymes released in saliva: Salivary Amylase and Lingual Lipase

Salivary Amylase - begins digestions of carbs

lingual lipase - beings digestion of lipids

glands:

1) Parotid (2) - “near ear“

2) submandibular (2) - lies along mandibular body

3) sublingual - lies at base of tongue

4) buccal - smaller/minor

TEETH - tear and grind food down

Primary dentition deciduous. teeth = 20

permanent dentition = 32

incisors = cutting

canines = tearing/piercing

premolars/molars = grinding

Crown - out portion covered w/enamel

root = embedded in jaw bone

cement = anchors root

dentin = boneline material under enamel

pulp cavity = blood/nerve supply

PHARYNX - passageway for food, fluids, and air

esophagus - muscular tube

• 10 inches

• passageway for food/drink to stomach

• enters stomach at CARDIAC SPHINCTER

• mucous cells produce a basic pH to protect from acid

mastication (chewing)

begins mechanical breakdown of food and mixes food with saliva

deglutition (swallowing)

invovles 2 phases

1) buccal - voluntary - forces BOLUS into pharynx

2) pharyngeal - esophageal Phase (involuntary ) - food is squeezed from pharynx into esophagus

stomach

• 50ml up to 4l volume

• continuse chemical breakdown of good

• changes BOLUS to CHYME when it leave

• CHYME exits thru phyloris sphincter into intestines

• 3 layers of smooth muscle help it churn. rest of GI tract only has 2 layers

in the pit image* parietal cells. blue. secretes HCI (hydrochloric acid)

• activates pepsinogen

• denatures proteins

• breaks down cell walls

• kills bacteria

in purple .chief cells. secretes enzymes

• pepsinogen

• lipase.

• lingual and gastric lipase break down lipids. furthers process

• pepsinogen is inactive protein enzyme. needs to be activated to pepsin. HCI activates this.

• HCI helps digests proteins

• pepsinogen breaks down amino acids into chuncks to digest

• HCI breaks down cell walls in veggies. cellulose breas down.

• we dont absorb cellulose

degestive process in stomach

• 3L of gastic juice

• protein is chemmicaly broken down- HCI changes pepsinogen into active pepsin enzyme

• lipase works on lipids

• digestion is only finished in small intestines

• very little nutrients is absorbed thru stomach wall except alcohol and drugs like asprin ← is a lipid like thing

small intestine (1-2L of intestinal juice secreted)

• digestion is finished and nutrients are absorbed

• starts at phyloric sphincter and ends at ileocecal value at Large Inestine

• 3 parts

  • duodenum

    • hepatopancreatic ampulla - a ducts joins to from liver (makes bile) and pancreas (pancreative juice). dumps all that stuff into small intestine

  • jeiunum - middle part

  • ileum - joins large intestine at ileocecal valve

small intestines are efficient at absorption

• circular folds in them that have villi

• villi - fingerlike projections (1mm)

  • lined with absorptive cells and goblet cells

  • in core of each have lacteal. these are capillary beds with lymphatic vessels

microvilli - on surface of absorptive cells → produces “brush border“ enzymes

• large intestines absorb some vitamines

LIVER - biggest interbal organs w/4 lobes

• hepatocytes - liver cells

• stores vtiamins and glucose as glycogen

• makes cholesterol

• filters out toxins majorly. but you can overexaust it

• makes clotting factors

• makes bile

• metabolizes amino acids and lipids for glycolysis (ATP). to prepare for glycolsis cellular

• break down old RBC - bilirubin (waste in feces)

• converts NH sub 3 (aminoa) to urea (filtered out of blood into urine)

GALLBLADDER - stores bile

• yellow-green alkaline solution

• stomach is very acidic though

• bile salts (fat emulsifier)

• bile pigments - bilirubin (waste product of heme)

• cholesterol, phospholipids and electrolytes

disorders

gallstones - crystallized cholesterol

jaundice - bile duct blockage or liver disease (skin turns yellow as bile pigments build in blood)

pancreas (gland) (1.5L pancreatic juice)

• HCOc- (raises pH). bicaronic ion

• proteases (protein enzymes). there are many types

• pancreatice amylase (carbs), lipase (lipids), nucleases. all in small intestine

• pancreatic islets - make hormones insulin and glucogon (can secrete this well blood sugar low). monitor

LARGE INTESTINE

• couple inches in diameter

• grames small

• 5-6 feet long

• does not absorb building blood nutrients

• absorbs water

• solid waste production

• anything not digesticed

• linied with goblet cells

• teniae coli and haustra are main features

• teniae coli = 3 bands of long muscle. tucks large intestine into pouches haustras. plays a role in moving stuff forwards in contractions to next pouch

• at end of small intestine it drops into large intestine into a vavle thing and appendix.

• if good bacteria is killed in large intestine

• appexdix can get infected and removed

• acceding colon takes a left turn across and turns about to colon.

• anal canal has two spincters

subdivision of large intestine

cecum - hangs below ileocecal valve appendix lymphoid tissue (role in immunity)

colon - ascending, transverse, descending, sigmoid

rectum - 3 folds

anal canal - internal and external sphincters

bacterial flora

• produces b vitamins and some K (clotting)

digestive process (10-12 hours)

• absorbs vitamins, water and some electrolytes

• no digestion or absorption of food

• haustral contractiosn and mass peristalsis moves contents

• defecation reflext - initiated by feces stretching rectal wall, sends signals to open internal sphicter (feel pressure)