module 5

gastrointestinal tract

continuous tube that extends from the oral cavity to the anus - mouth, pharynx, esophagus, stomach, small intestine, and large intestine

accessory organs

teeth, tongue, salivary glands, liver, gallbladder, and pancreas

ingestion

intake of food

digestion

mechanically or chemically with enzymes

digestive system functions

ingestion, digestion, absorption of nutrients, and defecation

defecation

waste elimination

deglutition

swallowing

oral cavity

ingestion, mechanical and chemical digestion and deglutition

swallowing

pharynx and esophagus

stomach

food is mixed with acidic gastric juice and chemical digestion continues

empties its contents into the small intestine

small intestine

assisted by secretions from the liver, gallbladder and pancreas

site of most chemical digestion

where most absorption occurs

liver

largest gland in the body

assists lipid digestion through the secretion of bile

bile

emulsifier

gallbladder

liver’s accessory

stores and concentrates bile

pancreas

gland

secretes pancreatic juice and bicarbonate to buffer the acids from the stomach

pancreatic juice

enzymes to chemically digest food in the small intestine

large intestine

responsible for the absorption of water from feces and the elimination of waste

regions of the small intestine

jejunum, ileum, and duodenum

digestive process begins

in the oral cavity - when we ingest food

food gets dissolved

by saliva from the salivary glands

chewing by teeth

formation of a ball of food - bolus

hard palate

formed by two palatine processes of the maxillae and two palatine bones

soft palate

composed of muscle

uvula

portion of the soft palate

rises during swallowing to prevent food from enetering the nasopharynx

nasopharynx

regions of the pharynx behind the nose

tongue

assists with chewing, swallowing, and pushing the bolus of food into the oropharynx

oropharynx

region of the pharynx posterior to the larynx.

laryngopharynx to what

esophagus

epiglottis

closes the glottis and prevents food from entering the larynx and trachea

oral cavity, pharynx, and gastrointestinal tract layers of tissue

mucosa, submucosa, muscularis mucosae, and serosa/adventitia

lined with stratified squamous

skeletal muscle in muscularis externa

saliva

contains water, mucus, and enzymes

dissolves food we eat so that we can taste and swallow it better

contains enzyme that initiates the digestion of starch

secreted into the oral cavity

intrinsic salivary glands

produce saliva

extrinsic salivary glands

3 pairs

located outside of the mouth

larger than intrinsic

3 extrinsic salivary glands

parotid glands

submandibular glands

sublingual glands

parotid glands

largest of the three extrinsic glands

located superficial to the masseter muscles

secrete saliva through the parotid ducts

parotid ducts

open near the upper molars on both sides of the mouth

submandibular glands

are the second largest of the three extrinsic glands

located near the mandible

submandibular ducts

secrete saliva onto the floor of the mouth, lateral to the tongue

sublingual glands

smallest of the extrinsic glands

located underneath the tongue

have a dozen small sublingual ducts

sublingual ducts

secrete saliva up into the mouth

just under the tongue

how many layers of tissue on the esophagus

four layers

mucosa esophagus

superficial epithelium - stratified squamous

layers of the mucosa

epithelium, lamina propria, and muscularis mucosa

muscilaris mucosa

smooth muscle

submucosa

connective tissue - combination of properties from areolar and dense irregular connective tissues

mucous glands are found here - helps move the bolus of food through the esophagus during swallowing

muscularis externa

top third - skeletal muscle

middle third - skeletal and smooth muscle

bottom third - smooth muscle - inner circular and outer longitudinal - cause peristalsis

peristalsis

involuntary, wave-like contraction and relaxation of muscles in the digestive tract. It propels food and liquid through the esophagus, stomach, and intestines.

esophagus most external layer

adventitia - extraperitoneal - the anatomical space or structures located outside or between the peritoneum (the lining of the abdominal cavity)

adventitia- loose connective tissue with collagen and elastin fibers

what happens once food enters the stomach

stored for a short time

mixed with gastric juice to form chyme

where does protein digestion occur

the stomach

Where is any carbohydrate digestion that began in the mouth inhibited by

acids of the stomach

lower esophageal sphincter

separates the esophagus and the stomach

muscle remains contracted at all times - except swallowing

prevents gastric juice from rising into the esophagus and damaging its lining

during swallowing

the lower esophageal sphincter relaxes and food enters the cardiac region of the stomach

fundus

small pouch on the left side of the stomach

where food is stored - after an hour it enters the body

body of the stomach

largest region of the stomach

stomach mixes and churns the food with gastric juice - becomes chyme

pylorus

third region of the stomach

connects to the duodenum of the small intestine

pyloric sphincter

controlls the movement of chyme from the pylorus to the duodenum

sphincter muscle

lesser curvature

smaller, concave surface of the stomach

greater curvature

larger, convex surface of the stomach

rugae

ridges inside the stomach

increase the storage capacity of the stomach

when stomach is empty- folds are larger

when the stomach is full - the folds flatten

how many liters can the stomach hold

4

mucosa of the stomach

simple columnar

gastric pits - gastric glands

cells linings the pits

secrete thick layer of mucus that protects the lining of the stomach

cells lining the glands of the stomach

secrete the different components of gastric juice, like pepsinogen and hydrochloric acid

muscularis externa of the stomach

smooth muscle

• circular

• longitudinal

• oblique

greater mixing and churning of food during digestion

outer layer of the stomach

serosa

composed of mesothelium (simple squamous epithelium) and areolar connective tissue

small intestine info and regions

site of most chemical digestion

duodenum, jejunum, and ileum

duodenum

attaches to the pylorus of the stomach

first 10 inches of the small intestine

retroperitoneal

begins at the pylorus, heads to the left side of the body, past the pancreas, and makes a sharp turn back toward the middle of the abdomen

pyloric spincter

controls how much chyme is entering the duodenum from the pylorus

what does the duodenum recieve

acidic chyme from the stomach, bile from the liver and gallbladder, and pancreatic juice from the pancreas

bicarbonate from pancreatic juice

buffers the avidic chyme

pancreatic juice

contains digestive enzymes that the small intestine uses to chemically digest carbs, proteins, and fats

bile from the liver and gallbladder

assist in fat digestion

emulsify fat

jejunum

second part of the small intestine

ileum

third part of the small intestine

attaches to the first segment of the large intestine - cecum

umbilical region of the abdominopelvic cavity

ileocecal valve

controls the movement of chyme from the ileum to the cecum

sphincter

pubic region

epithelium of small intestine

simple columnar

mucosa of small intestine

villi - finger like extensions

intestinal crypts - small invaginations

create more surface area- needed for nutrient absorptions

muscularis externa and outer layer of small intestine

2 layers of smooth muscle

serosa outer layer

absorptive cells

in the small intestine

have microvilli on their apical surface

create digestive enzymes called brush border enzymes and are responsible for the absorption of nutrients

goblet cells

secrete mucus to lubricate the chyme and protect the lining of the small intesine

lacteal

lymphatic capillary

aids in the absorption of fat

intestinal crypts

between villi, small invaginations of the mucosa

screte intestinal juice - aids in digestion

duodenal glands

in the duodenum

submucosa has

secretes buffers to neutralize the acidic chyme coming from the stomach

how does large intestine get its name

its diameter is larger than the small intestine

but it is shorter

cecum

cecum of the large intestine is connected to the ileum of the small intestine

ileocecal valve

controls the movmenet of chyme from the small intestine to the large intestine

vermiform appendix

attached to the cecum

small pouch that contains lympatic tissue

ascending colon

directly attaches to the cecum

ascends up the abdominopelvic cavity toward the liver

retroperitoneal

hepatic flexure

ascending colon turn to transverse colon

transverse colon

transcends across the abdominal cavity toward the spleen

splenic flexure

transverse colon turning to descending colon

descending colon

descends down the abdominopelvic cavity toward the left pelvis

retroperitoneal

sigmoid colon

as the colon enters the pelvis

s-shaped

retroperitoneal

they sit behind the peritoneum, which is the thin, continuous serous membrane that lines your abdominal cavity and covers organs like the stomach and liver.

which is higher hepatic flexure and splenic flexure

splenic flexure is higher because the position of the liver is lower in the abdominopelvic cavity than the spleen

rectum

retroperitoneal

descends down the middle of the pelvis

anal canal

final region of the large intesine

teniae coli

longitudinal bands of thickened smooth muscle

create tone in the large intestine

haustra

cecum and colon bulge into these structures

allow small amounts chyme to move through the colon in segments through a type of movement called haustral movements