Digestive System 2

What is the muscularis externis?

Two layers of smooth muscle separated by a second network of nerve cells

What is the inner layer of the muscularis externis?

Circular layer, constricts the lumen

What is the outer layer of the muscularis externa?

Longitudinal layer, shortens gut length

What is the purpose of the muscularis externa?

Mix and move the chyme

What is the enteric nervous system?

Two nerve cell networks from submucosa and muscularis externa

What does the enteric nervous system do?

Regulates gut secretions and mobility, not controlled by brain

What is the serosa/adventitia layer?

Fourth layer made of simple squamous epithelium and areolar connective tissue

What is the peritoneum?

Largest serous membrane in the body, in the abdomen

What is the parietal peritoneum?

Lines abdominal cavity wall

What is the visceral peritoneum?

Lines the external surface of digestive organs

What is the peritoneal cavity?

Cavity filled with serous fluid which lubricates mobile organs

What is mesentry?

A fused double layer sheet of parietal peritoneum that binds the intestines to the posterior abdominal wall, forms a route for blood vessels and nerves to enter and exit digestive organs

What are omenta?

Fused visceral peritoneum layers

What is the greater omentum?

Descends from the stomach and drapes over the small intestine and transverse colon to which it connects

What is the lesser omentum?

Extends between the liver and stomach

What does it mean to be retroperitoneal?

Organs are behind the peritoneum and serosa only cover the anterior side

What are some retroperitoneal organs?

Duodenum, pancreas

How is adventitia different from serosa?

No epithelium

What does the stomach do?

Stores, partially digests, mixes, regulates emptying of chyme

When is food called chyme?

When it enters the stomach

How much food do we want to enter the small intestine?

Only very small amounts at a time

Where is the stomach?

Left side of body

What is the cardinal region of the stomach?

Site where esophagus enters the stomach

What is the fundus of the stomach?

Part of stomach that rises above esophageal canal

What is the body of the stomach?

The middle, leftmost portion

What is the pyloric region of the stomach?

Inferior funnel shaped portion

What does the pyloric sphincter do?

Regulates the release of stomach contents in the small intestine

What is the pyloric sphincter?

Opening between stomach and small intestine

What is the inner oblique layer of muscle?

Unique to stomach, extra deep layer of muscularis externa, mixes chyme

What are rugae?

Many folds formed by the stomach mucosa to allow expansion

What are gastric pits?

Invaginations into stomach mucosa that form exocrine gastric glands

What are gastric glands?

Glands that secrete juices into the stomach lumen

What are the three types of gastric glands?

Chief cells, parietal cells, goblet cells

What are chief cells?

Cells that secrete inactive enzymes for protein and fat digestion

What are parietal cells?

Cells that secrete HCl to activate enzymes

What are enteroendocrine (G) cells?

Endocrine glands deep in gastric pits which secretes hormones into the blood

What do enteroendocrine cells do?

Regulate the activity of parietal cells and other digestive activity

What is the small intestine?

Tract from pyloric sphincter to ileocaecal valve, site of most digestion and absorption

What are the three parts of the small intestine?

Duodenum, jejunum, ilium

Where is the duodenum?

Short, beginning of small intestine, curves around pancreas

What does the duodenum do?

Most absorption, secretes alkaline mucosa to neutralize stomach acid, ducts of accessory organs enter here

Where is the jejunum?

Middle of small intestine

Where is the ilium?

Last part of small intestine

Where are Peyer’s Patches in the small intestine?

Ilium

What is muscle tone?

Partial state of contraction, all smooth muscle is usually like this

How long is the small intestine?

Duodenum is 25cm, the rest is 2.5m in life, 6m in death

What are enterocytes?

Simple columnar cells with many microvilli which cover most of the mucosa

Where are enteroendocrine cells located?

Stomach, glands in small intestine

What strategies does the small intestine have to increase surface area?

Plicae circulares, villi, microvilli

What are plicae circulares?

Many circular folds of the submucosa

What are villi?

Finger like projections on the mucosa containing blood and lymph capillaries

What do blood capillaries do in villi?

Provide oxygen, absorb nutrients

What are lacteals?

Lymph capillaries

What do lacteals do in villi?

Absorb fat, drain into cisterna chyli

What are microvilli?

The brush border on villi that are on absorptive cells

What is the difference between rugae and plicae circulares?

Rugae are for expansion, plicae circulares are to increase surface area

How do pancreatic secretions empty into the duodenum?

Pancreatic duct to hepatopancreaic ampulla OR accessory pancreatic duct

How do gall bladder secretions enter the duodenum?

Cystic duct to common bile duct to hepatopancreatic duct

How do liver secretions enter the duodenum?

Common hepatic duct to Common bile duct to Hepatopancreatic ampulla

What are the accessory organs?

Liver, pancreas, gallbladder