digestive system

digestive system

take in food, break down into nutrients for blood stream and lymph and rid the body of indigestible.

alimentary canal (GI tract)

the pathway of food through the body, the food directly travels through this canal

digestion

breaking down into small absorbable pieces

organs of the GI tract (pathway of food)

mouth - pharynx - esophagus - stomach - small intestine - large intestine - anal canal

accessory organs

teeth, tongue, salivary glands, liver, pancreas, digestive glands

ingestion

eating/taking in of food

propulsion

movement of food through the alimentary canal

peristalsis

major means of propulsion - alternating waves of muscle contraction

mechanical breakdown

chewing, mixing food with saliva, churning food in stomach

absorption

intake of nutrients into the blood or lymph

defecation

get rid of waste / indigestible

peritoneum

serous fleshy membrane that covers parts of the digestive system

visceral peritoneum

membrane that covers and protects organs

parietal peritoneum

covers the abdominal wall

peritoneal cavity

fluid filled space between parietal and visceral peritoneum, lubricates moving organs

mesentery

folding of peritoneum, extends from body wall to intestines.

• provides passageway from blood and lymph

• keeps organs in place

omentum (lesser and greater)

visceral peritoneum that hangs over organs (connects stomach to adjacent organs)

lesser omentum

attaches stomach to liver

greater omentum

covers small intestines like an apron (starts at stomach)

what are the four layers of the GI tract

(lumen is the center), mucosa, submucosa, muscularis externa, serosa

mucosa of the GI tract

simple columnar epithelium with two sublayers

GI tract tissue type of mouth, esophagus, and anus

stratified squamous epithelium

functions of GI tract mucosa

secretes mucus, absorb nutrients, protect against disease

three sublayers of mucosa

• epithelium - makes mucus and absorbs nutrients

• lamina propria - loose areolar connective

• muscularis mucosae - smooth muscle for small mvmts

plicae circulares

circular folds/villi make food absorption more efficient

submucosal layer of GI tract

• elastic tissue (allows lumen to stretch)

• contains blood and lymph supply to GI tract

• allows nerve innervation

muscularis externa of GI tract

• responsible for segmentation and peristalsis

• contains inner and outer muscular layers (form sphincters)

sphincter

ring of muscle that functions in opening or closing a certain tube or pathway

serosa layer of GI tract

outermost layer / visceral peritoneum

• prevents friction and binds organs to mesentery

blood supply of the digestive system

comes off the aorta

what are the three major arteries that come off the aorta

celiac trunk

superior mesenteric artery

inferior mesenteric artery

where does the celiac trunk supply blood

liver, stomach, spleen, pancreas, gallbladder

where does the superior mesenteric artery supply blood

small intestines and half of large

where does the inferior mesenteric artery supply blood

rest of large intestines

oral cavity direction

lips anteriorly, cheeks laterally, palate superiorly, tongue inferiorly, posterior continuous with oropharynx

mucosa of the mouth (tissue type)

keratinized stratified squamous (tough cells to resist abrasion)

palate of the mouth

form roof of mouth (2 parts)

• hard palate (bone/front of mouth)

• soft palate (skeletal muscle/back of mouth) - closes nasopharynx during swallowing

what is the tongue

composed of 4 interlacing’s of skeletal muscle / formation of bolus/saliva

what are the papillae of the tongue

taste buds / give tongue roughness

function of salivary glands

cleanses mouth - antibodies like IGA

moisten food

dissolve food chemicals for taste

amylase

beginning process of digestion for dietary sugars

parotid salivary gland

anterior to ear lobe (largest)

submandibular salivary gland

medial to body of mandible (produce most of saliva 70%)

sublingual salivary gland

under the tongue

• innervated by CNS (facial 7 and glossopharyngeal 9 )

mumps

inflammation of saliva glands caused by myxovirus

• common in kids

• spread through saliva

composition of saliva

• mostly water 95-97%

• slightly acidic 6.75 - 7.00

• IGa

• digests mainly starch

mastication

process of chewing

number of teeth

32

incisor teeth

chisel shaped for cutting

canines

pointy teeth to tear or pierce

premolars (bicuspids)

broad crowns with rounded cusps used to grind or crush

molars

broad crowns, rounded cusps, best grinders

tooth number 1

upper right molar

crown of tooth

exposed portion of tooth - covered in hard white enamel (hardest substance in the body)

root of tooth

portion beneath the gums - embedded in bone, connected to crown by neck

cement of tooth

calcified connective tissue

covers root and attaches it to periodontal ligament

periodontal ligament

anchors teeth into jawbone (gomphosis fibrous joint type)

pulp of tooth

soft tissue within teeth that houses blood, nerves and veins supply

dentin of tooth

bone like material under the enamel / makes up most of the tooth structure

pharynx

the throat

• allows passage of food, fluid and air

tissue type of pharynx

stratified squamous epithelium with mucus producing glands

pharyngeal constrictors

swallowing muscles

esophagus

flat muscular tube that runs from laryngopharynx to stomach (8 inches)

esophageal hiatus

where esophagus pierces diaphragm to reach the stomach

cardial orifice

where the esophagus joins the stomach

esophagus tissue type

stratified squamous

inferior gastroesophageal sphincter (cardial)

keeps orifice closed when food is not being swallowed

Superior gastroesophageal sphincter

closed during inspiration -> larynx, opens when swallowing food and drink

cardia part of the stomach

connects esophagus to stomach

fundus of the stomach

dome shaped region near the top of the stomach close to the diaphragm

body of stomach

midportion/majority of the stomach

pyloric portion of the stomach

end of the stomach, continuous with small intestine through the pyloric valve (controlling stomach emptying)

stomach

the temporary storage tank that starts protein digestion, converts bolus food to paste like chyme

rugae of the stomach

wrinkles in the stomach, formed when stomach is empty

allows for expansion

muscularis externa of the stomach

has an extra third layer

• inner oblique layer - mix, move and pummel chyme

mucosa layer of the stomach

simple columnar (with gastric pits)

dotted with gastric pits that lead to gastric glands (stomach juice formation - 3L a day)

where is the most gastric juice created

glands in the fundus and body of the stomach

which 4 cell types make juiced

• mucus neck cells

• parietal cells

• chief cells

• enteroendocrine cells

mucus neck cells

secrete mucus

parietal cells

secretes hydrochloric acid, pH 1.5-3.5, denatures proteins, activates pepsin/ kills many bacteria

chief cells

secrete pepsinogen concreted to pepsin, a protease enzyme

enteroendocrine cells

gastrin-> activates parietal cells to release HCL and chief to make pepsinogen, aids in relaxing pyloric sphincter = control emptying stomach

mucosal barrier

protects stomach, harsh digestive conditions require stomach to be protected from acid/bacteria

• thick layer of bicarbonate rich mucus made by liver

ulcer

protective mucus layer was destroyed / the protective layer in the stomach

b12 function

needed for absorption to mature

1.5L

stomach stretches to accommodate this amount

liver digestive function

produces bile

bile digestive function

helps digest fats in small intestines

gallbladder digestive function

stores bile

pancreas digestive function

pancreatic juices -> bicarbonate to neutralize stomach acid

liver anatomy

3lbs, 4 lobes

abdominal quad - upper right below diaphragm

falciform ligament

separates right and left lobe, suspends from diaphragm and anterior abdominal wall

right and left hepatic duct

merge together to form the common hepatic duct (which leaves the liver)

cystic duct

connects to the gallbladder

bile duct

formed by cystic and common hepatic duct (one way system) - empties into duodenum

liver lobules

6 sided structural and functional units, composed of plates and hepatocytes, filters/processes nutrient rich blood from GI tract

hepatocyte function

produce 9000 mL juice per day, perform detoxification - ex. coverting ammonia to urea

what does the portal triad in each corner of the lobule contain

arteriole - branch of hepatic artery - supplies blood

venule - branch of hepatic portal vein - supplies nutrient rich blood from GI tract

bile duct - receives bile from bile canaliculi, manufactures the bile then shipping it out at a bile duct depending on which corner

sinusoid capillary

spokes of the lobule, blood from both hepatic portal vein and hepatic portal artery proper percolates -> flow through the capillary veins

central vein

filtered blood of the liver leave through this