Anatomy 2120 Final

Two categories of the digestive system

Accessory digestive organs and the organs of the gastrointestinal (digestive) tract

Digestive tract

Continuous muscular tube composed of skeletal muscle and smooth muscle

Organs of the digestive tract

Mouth, pharynx, esophagus, stomach, small intestine, and large intestine

Accessory digestive organs

Teeth, tongue, gallbladder, and digestive glands (salivary glands, liver, and pancreas)

Functions of the digestive system

Ingestion, mastication, propulsion, mixing, secretion, digestion, absorption, and excretion

Peritoneum

Membrane which lines the walls and organs of the abdominal cavity

Makes up the peritoneum

Visceral peritoneum and parietal peritoneum

Visceral peritoneum

Covers the external surface of the organs within the abdominal cavity

Parietal peritoneum

Lines the internal surface of the walls of the abdominal cavity

Peritoneal cavity

The space between the two layers of the peritoneum; filled with peritoneal fluid

Mesentaries

Holds many of the organs of the abdominal cavity together; a fused double layer of peritoneum that extends from the body wall to a digestive organ

Retroperitoneal

Other organs of the abdominal cavity that are not suspended to a mesentary

Example of a retroperitoneal organ

Kidney (Severt specifically said to put this on quiz)

Associated structures of the oral cavity

Lips, cheeks, palate, tongue, teeth, and salivary glands

Lips (labia) and cheeks

Composed mainly of muscle; orbicularis oris (lips) and buccinator (cheeks); involved with mastication and speech

Hard palate

Forms the “roof” of the mouth; tongue forces food against this when chewing (also plays a role in speech)

Soft palate

Posterior to the hard palate; composed of skeletal muscle (closes off the nasopharynx when we swallow)

Tongue

Aids in chewing, swallowing, and speech

Salivary glands

Produce and secrete saliva

Functions of saliva

Cleanses mouth, dissolves food chemicals so they can be tasted, contains the enzyme salivary amylase (begins chemical breakdown of starchy foods)

Three pairs of salivary glands

Parotid, submandibular, and sublingual glands

Parotid glands

One located anterior to each ear

Submandibular glands

Inferior to the mandible

Sublingual glands

Inferior to the tongue

Pharynx

“throat”, food from the oral cavity passes through the fauces into the oropharynx, food then passes into the laryngopharynx

Esophagus

Food passes from the laryngopharynx into the esophagus (carries food into the stomach)

Does digestion start in the esophagus?

No

Stomach

Food is broken down mechanically and chemically; 3 layers of smooth muscle mechanically digest the food; gastric glands (located in the ling of the stomach) release substances that chemically digest the food

Major structures of the stomach

Cardiac sphincter, cardiac region, fundus, body, greater curvature, lesser curvature, pyloric region, pyloric sphincter, rugae

Gastric pits

Found in the epithelial lining of the stomach

Gastric glands

Gastric pits are the openings for the _______ (produce gastric juice)

pH 1.5 to 3.5

pH level of the highly acidic gastric juice that contains chemicals to aid in chemical digestion

What substances produce gastric juice?

The cells that form the gastric glands

Cells of the gastric glands

Mucous cells, parietal cells, chief cells, and endocrine cells

Main function of small intestine

Absorption

3 parts of small intestine

Duodenum, jujenum, ileum

Small intestine

Digestive organ where digestion is completed and nearly all absorption; extends from the stomach to the large intestine; gets shorter in life due to muscle tone (~11 feet)

Duodenum

Shortest and first portion of the small intestine; wraps around the head of the pancreas; contains Brunner’s gland

Brunner’s gland

Produces an alkaline substance that neutralizes acidic chyme

Jejunum

Middle portion of small intestine, extends from duodenum to ileum, makes up about half the length of the small intestine

Ileum

Last portion of the small intestine (joins the cecum of the large intestine)

What type of capillaries allow for increased absorption in the small intestine?

Fenestrated capillaries

Modifications that increase the surface area of the small intestine

Overall length of the small intestine, the lining of the small intestine is folded (circular folds) and have tiny fingerlike projections called villi, cells contain microvilli

Liver

Second largest organ in the body, largest gland in the body, located in the right upper quadrant

Major structures of the liver

right lobe, left lobe, caudate lobe, quadrate lobe, hepatic porta

Functions of the liver

Stores glucose as glucagon, takes waste products out of the blood, hepatocytes of the liver produce bile (stored in the gallbladder)

Ducts associated with the liver

Common hepatic duct, right hepatic duct, left hepatic duct, cystic duct, and common bile duct

Common hepatic duct

Carries bile away from the liver, formed by the union of the right and left hepatic ducts

Cystic duct

carries bile away from the gallbladder, joins with the common hepatic duct to form the common bile duct

Pancreatic duct

Carries HCO₃ and enzymes, joins the common bile duct to make the ampulla of Vater; exocrine pancreatic secretions exit the pancreas

Ampulla of Vater

Drains via the major duodenal papilla into the duodenum of the small intestine

Pancreas

Located in the abdomen partially behind the stomach; both an endocrine and exocrine gland

Substances produced by the endocrine portion of the pancreas

Insulin and glucagon

Substances produced by the exocrine portion of the pancreas

Enzymes that aid in digestion of carbohydrates, fats, and proteins in the small intestine; HCO₃ ions that neutralize acidic chyme in small intestine

Large intestine

Extends from the small intestine to the anus

Functions of the large intestine

Absorption of water (absorption of nutrients completed in the small intestine), elimination of waste products (feces)

Divisions of the large intestine

Cecum, colon, rectum, and anal canal

Cecum

First part of large intestine, joins with the ileum of small intestine (ileocecal junction), has appendix attached to it

Appendix

Aka vermiform appendix, plays a role in immunity and can collect bacteria

Colon

Consists of the ascending colon, right colic (hepatic) flexure, transverse colon, left colic (splenic) flexure, descending colon, sigmoid colon

Rectum

Portion of large intestine located between the sigmoid colon and anal canal, stores feces

Anal canal

Last 2-3 cm of the digestive tract, extends from the rectum to the anus (opening of the anal canal to “outside” world), surrounded by internal and external anal sphincters

Internal anal sphincter

Composed of smooth muscle (involuntary)

External anal sphnicter

Composed of skeletal muscle (voluntary)

Soft palate

More muscle than bone

Hard palate

“Roof” of the mouth, made up of bone

Uvula

Made up of the soft palate

Esophagus

Continuation of laryngopharynx once out of the pharynx, runs along the thoracic aorta

Cardiac sphincter (lower esophageal sphincter)

Where the esophagus meets the stomach, controls the amount of food going into the stomach, STRUCTURE

Cardiac region (of the stomach)

REGION

Greater curvature (of the stomach)

Bigger, on the outside, left side by spleen

Lesser curvature (of the stomach)

Right side, by the liver

Pyloric region (of the stomach)

Where the stomach gets narrower

Pyloric sphincter (of the stomach)

Where the stomach meets the duodenum

Rugae (of the stomach)

Folds that help increase surface area for mixing

Duodenum (of the stomach)

Next to pancreas

Major duodenal papilla (of the duodenum)

Tiny opening that aids in the transport of bile

Jejunum (of the small intestine)

Squiggly part of the small intestine; middle part of the small intestine

Ileum (of the small intestine)

Last part of the small intestine that connects to the large intestine by way of the cecum

Ileocecal valve

Prevents backflow

Plicae circulares (circular folds)

Contain villi and microvilli; increase surface area

Villi

Increase surface area for digestion

Microvilli

Small projections off of villi that increase surface area

Cecum (of the large intestine)

“Pouch”; first part of large intestine, can be green from bile

Vermiform appendix

Has lymphatic tissue and serves immune functions

Colon (of the large intestine)

Largest portion of the large intestine

Ascending colon (of the large intestine)

Moves upward

Right colic (hepatic) flexure (of the large intestine)

Where the colon turns into the transverse colon

Transverse colon (of the large intestine)

Runs horizontally

Left colic (splenic) flexure (of the large intestine)

Where the colon turns into the descending colon

Descending colon (of the large intestine)

Moves downward toward the sigmoid colon

Sigmoid colon (of the large intestine)

Little squiggle at the bottom of the large intestine before the rectum

Haustra (of the large intestine)

“Bulges” of the colon

Teniae coli (of the large intestine)

Smooth muscle that runs the length of the colon

Epiploic appendeges (of the large intestine)

Chunks of fat hanging off of the large intestine

Rectum (of the large intestine)

Where the feces is stored

Anal canal

Where the feces exits the body

Parietal peritoneum

Lines the inner walls of the abdominal cavities

Visceral peritoneum

Lines the surface of the organs

Peritoneal cavity

Space around the peritoneum filled with peritoneal fluid