anatomy digestive system

mucosa

innermost layer of tissues, made up of epithelial layer (usually columnar cells) and lamina propria- loose CT rich in blood and lymph vessels, contains sometimes some smooth muscle, glands, or lymphoid tissue

submucosa

layer of tissue, loose connective tissue, contains Meissner's nerve plexus which is autonomic nerve supply to GI, may also contain galnds and lymphoid tissue

muscle layer

layer of tissue that usually consists of smooth muscle, internal layers- generally circularly arranged, external layer- generally longitudinal, myenteric plexus- major GI nerve supply

serosal layer

outermost tissue layer, also called visceral peritoneum, consists of loose CT with adipose tissue

oral cavity

also called mouth, bounded superiorly by hard and soft palate, bounded laterally by cheeks, bounded inferiorly by extrinsic muscles of tongue; vestibule, oral cavity proper, lips, hard palate, soft palate, fauces, tongue

vestibule

part of oral cavity, bounded externally by the cheeks and lips and internally by the teeth and gums

oral cavity proper

area within the boundary of the teeth and gums, extends from the vestibule to the fauces

lips

important in speech and eating, fleshly folds surrounding the orifice- outside covered by stratified squamous keratinized epithelium- inside by a mucous membrane; labial frenulum- fold of mucous membrane attaching each lip to the gum

labial frenulum

fold of mucous membrane attaching each lip to the gum

hard palate

formed by palatine processes of the maxillary bones and palatine bones

soft palate

posterior to the hard palate- formed by muscle and covered by mucous membrane, contains uvula

uvula

finger-like process hanging from the inferior posterior part of the soft palate

fauces

entrance to pharynx from the oral cavity area enclosed by two lateral muscular folds (skeletal muscle) coursing inferiorly from the soft palate, sometimes referred to as tonsillar pillars, palatine tonsils

tongue

skeletal muscle covered by mucous membrane
- taste regions: sweet- tip, sour- lateral sides, bitter- posterior aspect, salty- everywhere

extrinsic muscles of tongue

hyoglossus, genioglossus, styloglossus, and palatoglossus (move tongue from side to side and in and out)

intrinsic muscles of tongue

originate and insert within the tongue itself, these alter size and shape of the tongue

lingual frenulum

fold of mucous membrane attaching inferior portion of the tongue to the floor of the mouth

anklyoglossia

tongue tied, when frenulum is too short and restricts movement of the tongue

filiform papillae

little cone-like projections on the tongue, mostly over anterior 2/3s of tongue, no taste buds, most numerous

fungiform papillae

small mushroom shaped projections scattered over the surface of the tongue, contain taste buds (most of them)

circumvallate papillae

like tiny guard towers arranged in a row shaped like a 'v' on the posterior surface of the tongue, these all contain taste buds and are located in the region of the tongue most sensitive to bitter taste

salivary glands

secrete saliva (between 1000 and 1500 mls each day), 99.5% H2O- medium for dissolving food, 0.5% solutes including; salts, sodium and potassium, phosphates and bicarbonates, some organic waste products are eliminated in the saliva, some proteins (mucin), enzymes (lysozome)

salivary amylase

initiates breakdown of carbohydrates- this enzyme will continue to act until it is inactivated by stomach acids

buccal glands

tiny glands within the mucous membrane of the oral cavity, these secrete a small amount of saliva but the majority is from the 3 pairs of salivary glands

parotid gland

almost completely serous producing, located just deep to the skin in an area anterior to the ear, overlies masseter muscle, enters oral cavity in vestivule just lateral to upper molars via Stensen's duct

submandibular gland

both mucous and serous secreting, located beneath the base of the tongue in the posterior floor of the oral cavity, enters oral cavity via Wharton's duct just lateral of the midline of the floor of the oral cavity proper- just posterior to the inferior central incisors

sublingual gland

located anteriorly to the submandibular gland, opens via several ducts into the floor of the oral cavity just below the anterior part of the tongue

teeth

dentes, located in sockets of alveolar processes of the mandible and maxillae, the alveolar processes are covered by the gingivae which extend into the sockets, the sockets are lined by dense fibrous connective tissue which secures the teeth in position and acts as a shock absorber (peridontal ligament)

peridontal ligament

dense fibrous connective tissue that secures the teeth in position and acts as a shock absorber

pyorrhea

inflammation of the peridontal ligament and adjacent gums

esophagus

muscular tube- 25 cm or 10 inches long, begins at inferior portion of laryngopharynx and continues to stomach passing thru mediastinum posterior to heart and just anterior to the vertebral column, mucosa, submucosa, muscular layer, tunica adventitia

stomach

curved enlargement of the GI tract immediately below the diaphragm, serves as a holding tank between esophagus and small intestine
- slightly to left of midline of bottom of rib cage, varies from individual to individual
- each breath changes position of the diaphragm and causes the stomach to move some, also since the stomach has such an incredible ability to increase in size the area occupied can vary from about the size of one's fist to ???

lower esophageal sphincter

separates stomach from esophagus, a physiological rather than an anatomical sphincter

pyloric sphincter

sphincter separating stomach from duodenum, stomach allows food to enter to rest of the GI tract at a slower pace thus allowing one to eat less frequently, movement of food into the duodenum is controlled by the pyloric sphincter

pylorospasm

in infants, failure of muscle fibers to open correctly

pyloric stenosis

a narrowing of the pyloric valve, hypertrophy of the sphincter

anatomy of stomach

cardiac region, fundus, body, greater curvature, lesser curvature, pylorus, sphincters

rugae

large folds of mucosal layer of stomach which allows for large changed in stomach size, disappear when stomach becomes distended

gastric glands

pits in mucosal epithelium of stomach

mucous glands

scattered throughout stomach mucosa, they are the only type of gland in the cardiac region

mucous cells

secrete lubricating mucous which protects cells from enzymes and acid in gastric juice, also secrete intrinsic factor for absorption of vitamin B12

parietal cells

secrete HCl

zymogenic cells

chief cells, secrete enzyme pepsinogen which is activated by HCl to form pepsin (breaks specific peptide bonds)

chyme

liquid that stomach contents are turned into

duodenum

first portion of small intestine, c-shaped, 12 inches long, mixed function of digestion and absorption, receives secretions of pancreas, liver, and gallbladder

crypts of lieberkuhn

tiny glands which run down between the villi in duodenum, where many digesting enzymes are produced

brunner's glands

glands in submucosal layer of duodenum, its secretions also chyme to become alkaline

pancreas

a thin flat elongated organ which lies posterior to the greater curvature of the stomach, greater part lies within the concavity formed by the duodenum

islets of langerhans

small clusters in pancreas, have an endocrine function and secrete glucagon and insulin into the bloodstream

acini

clusters in pancreas which have an exocrine function and secrete pancreatic juice (digestive enzymes destined for the duodenum)

main pancreatic duct

where pancreatic juice empties, this duct joins the common bile duct fro the liver and gallbladder and empties into the duodenum via the ampulla of vater which is located on an elevation of the mucosa called the duodenal papilla

liver

largest gland, one of largest organs, located immediately below diaphragm on right side
- has large right and left love and smaller quadrate and caudate lobes
- composed of microscopic hepatic lobules composed of radially arranged plates of hepatic cells surrounding a central vein, these plates are separated by hepatic sinusoids which are modified blood vessels, these contain some phagocytic Kupffer cells, at each corner of the hexagon is a portal triad which consists of branches of the portal vein, hepatic artery, and bile duct
- blood flows from portal vein and hepatic artery thru sinusoids toward the central vein, provides oxygenated blood to the cells and allows them to act on blood coming from the digestive tract
- bile flows toward branches of the bile duct within the triad
- performs many complex and vital functions- manufactures plasma proteins, kupffer cells phagocytose bad blood cells, bacteria, etc., hepatocytes manufacture enzymes that breakdown harmful compounds, serves as large storage facility for glycogen which can be transformed to glucose, manufactures many enzymes for metabolism, manufactures and secretes bile

falciform ligament

separates right and left liver lobes

bile

important for emulsification and absorption of fats in the intestine, contains some waste products from the circulation

gallbladder

pear-shaped organ on the underside of the liver, function is to store and concentrate the bile
-sphincter of oddi is closed when no food is in duodenum, causes bile to back up and flow into gallbladder
- much of fluid of bile is reabsorbed nito the blood via the mucosa
- when food enters duodenum, it produces a hormone called cholecystokinin which travels via blood to the gallbladder causing the muscles to contract
- cystic duct is from gallbladder to common hepatic duct where they unite to form the common bile duct

jejunum

primary function is absorption of food materials into blood, proximal 2/5ths of small intestine not including duodenum (1st 12 inches), higher in abdomen, wider in diameter, thicker wall, more vascular and more red, more rapid and vigorous peristalsis

ileum

function is absorption of food materials into blood, distal 3/5ths of small intestine, more fat in mesentery, more branching of blood vessels

large intestine

about 5 feet lone, extends from ileum to anus, 4 major divisions (cecum, colon, rectum, anal canal)
- functions: some minor absorption (water and electrolytes), formation and storage of fecal matter until it can be expelled

ileocecal valve

at junction of ileum and cecum, allows food to pass into large intestine, but not back into small

vermiform appendix

has a variable position on the cecum, wormlike hollow appendage, has no known function, wall contains lots of lymphoid tissue, inflammation= appendicitis

colon

part of large intestine, 4 parts: ascending, transverse, descending, sigmoid

peritoneum

largest serous membrane in body, divided into visceral peritoneum and parietal peritoneum, between these is parietal cavity

lesser omentum

serosa between liver and stomach

greater omentum

large fold that overlies most of abdominal contents anteriorly, passes from greater curvature of stomach down and back up to the transverse colon, contains a great deal of lymph nodes and adipose tissue- helps to prevent the spread of infection in the abdomen

haustra

segments in large intestine

teniae coli

3 discrete bands of longitudinal layer of smooth muscle in large intestine

appendices apiploicae

localized collections of fat on outer wall of large intestine