bio lab 15

digestive system

what is the inner lining of the digestive tract called? what are the 3 layers?

mucous membrane

• #1: epithelial layer

• #2: connective tissue layer (lamina propia)

• #3: muscle layer (muscularis mucosa)

What type of epithelium lines non-absorptive regions of the GI tract?

non- keratinized stratified squamous epithelium

• found in mouth, pharynx, larynx

What type of epithelium lines absorptive/secretory regions of the GI tract?

simple columnar epithelium with goblet cells (musocus producing cells)

• large intestine, small intestine

what is the lamina propia composed of? what is its function

composed of areolar connective tissue with lymph nodules, blood vessels and lymph vessles

• nourishes and supports the epithelium

• connects the epithelium to the muscularis mucosae

what is the muscularis mucosae composed of? what is its function?

• third layert of mucosa, composed of smooth muscle

• creates the folds in the stomach and the large intestine

what is the submucosa composed of? what is it’s function?

composed of areolar connective tissue, contains many blood and lymph vessels

• binds the mucosa to the muscle (muscularis) layer

What change occurs in the muscular layer (muscularis) along the esophagus

upper GI tract: composed of skeletal muscle (voluntary, chewing)
lower GI tract: composed of smooth muscle (involuntary)

What are the 2 layers of the muscularis? what is the function of these 2 layers?

• inner circular smooth muscle layer

• outer longitudinal smooth muscle layer

function: the muscle fibers contract to cause the mixing and propulsion of food = peristalsis

what is the peritoneum of the GI tract? what is it composed of?

• this is serous membrane that lines the walls and covers the outside of most abbominal organs

• it is a double layered membrane with a layer of simple squamous epithelium and a layer of areolar connective tissue

what are the two layers of the peritoneium?

visceral peritoneum - covers some organs

parietal peritoneum - lines the wall of the abdominal cavity

what is between rhe parietal and viscaeral peritoneum?

serous fluid

• reduces friction

• keeps the membranes moist and slippery

what are retroperitoneal organs?

organs that are only covered by the visceral peritoneum on thier anterior surfaces are considered to be retroperitoneal

what are the 4 retroperitoneal organs

• duodenum

• pancreas

• ascending colon

• descending colon

what are the tissue (s) that make up the serosa

double layered membrane composed of…

• simple sqamous epithelium

• areolar connective tissue

what are the tissues that make up the musuckar layer/ muscularis?

inner layer of circular smooth muscle

outer layer of longitudinal smooth muscle

what tissues makeup the submucosa?

areolar connective tissue with blood vessels and lymphatic vessels

what tissue makes up the muscularis mucosae

smooth muslce (forms the ridges/ folds in the stomach)

what tissues make up the lamina propia?

areolar connective tissue with blood vessels, lymphatic vessels, and lymphatic nodules

what tissues makeup the mucous membrane

composed of 3 layers

• simple columnar epithelium (epithelial layer )

• areolar connective tissue (CT layer)

• smooth muscle (muscle layer)

what is digestion?

the act of breaking down food mechanically or chemically into smaller molecules, these molecules diffuse past the epithelial cells lining the GI tract into the blood stream

where does ingestion take place?

the mouth

what structures form the floor, slides and roof of the oral cavity

the tongue forms the floor, the lips and cheeks form the walls, and the hard + soft palates form the roof of the oral cavity

what are the 4 structures within the oral cavity

• teeth

• gums (gingiva)

• ducts of salivary glands

• uvula

what are the 3 accessory organs of the mouth

• teeth

• tongue

• salivary glands

what is a bolus ?

a soft mass of chewed food mixed with saliva that is ready to swallow

descrbie the structures involved in the movement of a bolus

skeletal muscle contractions of the oropharynx and pharyngeal pharynx push the bolus into the espohagus

hard palate function

forms the anterior roof of the mouth, separates the oral cavity from the nasal cavity

soft palate function

forms the posterior roof of the mouth, closes off the nasal cavity during swallowing and assists in speech

uvula function

closes off the nasopharynx during swallowing, aids in speech + gag reflex

tongue

moves food for chewing and swallowing, aids in speech and taste and forms the floor of the oral cavity

lingual fernulum

a thin fold of tissue under the tongue that anchors the tongue to the floor of the mouth, limits tongue movements

function of the incisors

chiseled shaped teeth that cut food

function of the canines

sharp teeth that tear food

function of the premolars

flattened teeth with a rigid surface that grinds food down

function of the molars

broad, flat teeth with a rigid surface that grinds food thoroughly

gingiva function

aks : gums

• firm tissue tgat surrounds and protects the teeth and tooth sockets

partoid gland

largest salivary gland, secretes the enzyme salivary amylase to begin the digestion of starch

sublingual gland function

salivary gland beneath the tongue, secretes mucus for lubrication

submandibular gland function

located below the jaw, secretes mucus for lubrication and the enzyme salivary amylase for the digestion of starch in the mouth

pharynx function

passageway for food and air

• directs food to the esophagus and air to the larynx

nasopharynx function

upper part of the pharynx, located behind the nasal cavity, allows for the passage of air

oropharynx function

middle part of the pharynx, behind the oral cavity, allows for the passage of food and air

laryngopharynx

lower part of the pharynx,leaing to the espoghagus, directs food to the esophagus and air to the larynx

esophagus function

a muscular tube that connects the pharynx to the stomach, allows for the passage of food from the laryngopharynx to the stomach with the help of perastalsis

upper esophageal sphincter vs lower esophegeal sphincter

upper

• a ring of skeletal muscle at the top of the esophagus that controls the passage of food from th pharynx to the stomach

lower

• a ring of smooth muscle at the bottom of the esophagus that prevents contents from the stomach refulxing back into the esophagus

what are the 4 main regions of the stomach

• cardia

• fundus

• body

• pylorus

pyloric sphincter

a sphincter composed of smooth muscle located at the junction of the pylorus and the duodenum, regulates the passage of the chyme into the small intestine

what type of epithelium lines the stomach?

simple columnar epithelium

how and where are gastric pits formed, what

folds in the mucosa create pits which extend down into the lamina propia

• these pita are line with a secretory epithelium called gastric glandss

what are the 3 exocrine gland cells in the gastric glands? where is it secreted? what does it form?

3 exocrine gland cells

• chief cells

• parietal cells

• musocus neck cells

these all secrete various substances into the lumen of the stomach to form gastric juice

how does the muscularis layer of the stomach differ from the rest of the GI tract?

the muscularis of the stomach contains an additional layer called the inner oblique muscle layer

stomach function

serves as a temporary holding site for food, site of the mechanical and chemical breakdown of food

carida function

region of the stomach that the esophagus enters, recives food from the esophagus

fundus function

superior region of the stomach that holds food and gas

body of the stomach function

large, central region of the stomach that is the site of mixing and secretion of substances from the exocrine cells of the gastric glands

pylorus function

inferior region of the stomach that leads into the duodenum, allows for the passage of chyme into the small intestine

lesser vs greater curvature of the stomach

lesser

• shorter, more concave side of the stomach, suite of attachment for the lesser omentum

greater

• larger, more convex side of the stomach, site of attachement for the greater omentum

gastric folds of the muscoa (rugae) function

longitudinal folds of the mucosa that are formed when the stomach is empty, allow the stomach to expand when filled with food

lesser omentum

a serous membrane that extends from the lesser curvature of the stomach to the liver, attaches and supports the stomach and liver

greater omentum

a serous membrane that extends from the greater curvature of the stomach to cover the intestines, supports, protects, and cushions the intestines

pyloric sphincter

a smooth muscle sphincter located at the junction between the lyorus and the duodenum, allows for the passage of chyme into the small intestine

what type of organ is the pancreas? where doe sit release it’s secretions

the pancreas is a secondary digestive organ

• it releases it’s secretions in to the duodenum of the small intestine

what is the other name for the accessory duct of the pancreas? where does it release it’s secretions?

duct of Santorini

• empties its secretions directly into the duodenum

what 2 structures for the hepatopancreatic ampulla? what is the specific site it empties into the duodenum?

• formed by the union of the pancreatic duct and the (common) bile duct

• empties into the duodenum at the major duodeneal papilla

what are the 4 substances foud in pancreatic juice

• enzymes

• salt

• water

• sodium bicarbonate

list 3 enzymes of the pancrease in adition to tripsin

• pancreatic amylase

• pancreatic lipase

• chymotripsinogen

What prevents pancreatic enzymes from digesting the proteins of the pancreas?

pancreatic enzymes are secreted as inactive zymogens, that are only activated in the small intestine, preventing the digestion of the pancreas

pancrease function

an acessory organ that secretes digestive enzymes and bicarbonate into the duodenum to aid in digestion + to neutralize acids

accessory duct of the pancreas function

small pancreatic duct that drains pancreatic secretions directly into the duodenum

pancreatic duct function

carries pancreatic secretions and forms with the (common) bile duct to then empty the secretions into the duodenum

liver function

a secondary digestive organ that receives blood from the absorptive areas of the GI tact via the hepatic portal vein and processes, stores and coverts nutrients + produces bile

what specific cell carries out the livers digestive function ? what does it secrete

hepatocytes carry out the livers digestive function, which secrete bile

what is the function of bile?

bile emulsifies lipids (no enzymatic action)

• breaks up larger lipid droplets into smaller lipid droplets, which creates a large SA for digestion via lipase (lipase breaks down lipids)

gallbladder function

stores bile, and removes water from the bile to make it more concentrated. it then releases the bile into the bile duct where it used for fat digestion

cystic duct

connects the galbladder to the common hepatic duct, allowing bile to move to and from the gallbladder

(common) bile duct function

formed by the union of the commin hepatic duct + the cystic duct, carries bile from the hepatopancreatic ampulla for release into the duodenum

hepatopancreatic ampulla function

junction where the common bile duct and the pancreatic duct join to release bile + pancreatic enzymes into the duodenum

major duodenmal papilla

the opening in the duodenum where the hepatopancreatic ampulla releases bile and pancreatic enzymes into the small intestine

what is the epithelial layer of the small intestine?

simple columnar epothelium with absorptive cells and goblet cells

what are the 2 glands in the smsll intestine that secrete mucus? where are they?

#1: interstitial cells

• lines the crevices in the mucosa

• secrete mucus, hormones and lysosomes

#2: duodenal glands

• located in the submucosa

• produces mucus

3 structures of the small intestine that increase the SA for exposure to nutrients

#1: circular folds

• located in the muscosal layer

#2: interstitial villi

• fingerlike projections of the mucosa that are covered by the absorptive columnar epithelial cells

#2: microvilli

• located on the apical (free) surface of columnar cells

duodenum function

the first part of the small intestine, recieves bile, pancreatic secretions and chyme for digestion

jejenum function

middle part of the small intestine, is the primary site of nutrient absorption

ileum function

last part of the small intestine that absirbes remaining nutrients and connects to the large intestine

ileal orfice (ileoceceal sphincter)

site where the ileum joins to the large intestine, composed of a ring of mooth muscle, regulates the flow of chyme into the large intestine

mesentry function

a fan shaped fold of the peritoneum that suspends the ileum and jujenum from the posterior abdominal wall

ciruclar folds of the small intestine

located in the mucosal layer, increase the surface area of the small intestine for exposure to nutrients

cecum fucntion

first part of the large intestine, receives materials from the ileium through the ileocecal sphincter, and passes that material to the colon

vermiform appendix

contains a cluster of lympatic nodules, attaches itself to the cecum

colon funciton

involved in the absoption of water, secretions from other parts of the GI tract + hormones, is responsible for the formation + expulsion of feces

aascending colon function

right side of colon, absorbs water, secretions from other parts of the GI tract + hormones, involed in the formation + expulsion of feces

transverse colon

crosses the abdomen L to R, absorbs water, secretions from other areas of the GI tract, + hormones, involved in the formation + expulsion of feces

descending colon

left side of the abdomen, absorbs water, secretions from other areas of the GI tract, + hormones, involved in the formation + expulsion of feces

sigmoid colon

S-shaped area of the colon that joins to the rectum to deliver feces

rectum

straight line section of the large intestine that stores fecal mater before elimination

anus

opening at the end of the digestive tract, allows for the elimination of fecal mater from the body

internal anal sphincter

composed of involuntary smooth muscle that maintains the closure of the anus, and relaxes it during defication

external anal sphincter

composed of voluntary skeletal muscle, allows for the concious elimination/ release of feces

mesocolon

serosa of the large intestine that connects the transverse colon and the sigmoid colon to the posterior abdominal wall

teniae coli

3 thickened longitudinal muscle bands of the colon that help form the hasturae