Anatomy Unit 3: Digestive system

Ingestion

Takes in food and drinks

Digestion

Breakdown of food into small structures and molecules and contains Mechanical digestion; breakdown by teeth, tongue, and muscles and Chemical digestion; breakdown using enzymes.

Motility

Movement of food and drinks

Secretion

Production and release of products to aid digestion

Absorption

Movement of nutrients and water across GI tract into blood and lymph vessels

Elimination

Gets rid of waste

What are the two types of Digestion?

Mechanical digestion = physical breakdown by teeth, tongue, muscles

Chemical digestion = breakdown using enzymes

Functions of the Digestive System?

Ingestion

Digestion

Motility

Secretion

Absorption

Elimination

Gastrointestinal (GI) tract

(also called digestive tract or alimentary

canal) is a tube formed by the following main digestive organs

Main Structures of the Digestive System

• Oral cavity

• Pharynx

• Esophagus

• Stomach

• small intestine

• large intestine

• Rectum

• Anus

Accessory digestive organs

Are not part of the digestive tract but are connected to it and assist in digestion.

Accessory Structures of the Digestive System

• Salivary glands

• Teeth

• Tongue

• Liver

• Gallbladder

• Pancreas

Mastication

Is the movement performed by teeth and tongue in the oral cavity to mechanically break down foods and mixing it with the saliva

Swallowing

is the movement performed by tongue and pharynx to push foods and drinks in the esophagus

Churning

Is the squeezing that occurs in the stomach to mechanically breakdown food and mixing it with digestive juices

Segmentation

Is the rhythmic movement of GI tract to mix food with digestive enzymes. Does not produce movement forward. Occurs mainly in small intestine

Peristalsis

Is made by waves of contractions along the GI tract (esophagus to anus) that push the material forward.

Motility in the GI Tract

Mastication

Swallowing

Churning

Segmentation

Peristalsis

Peritoneum

Abdominopelvic cavity is lined with moist serous membrane called

peritoneum that holds digestive organs in place through a series of

folds called mesenteries that contain blood vessels and nerves.

What is the Peritoneum made of?

• Parietal peritoneum lines inside of abdominal cavity

• Visceral peritoneum covers surface of abdominal organs (also known as

serosa)

• Peritoneal cavity is between peritoneal layers and contains serous fluid

Intraperitoneal organs

are completely surrounded by visceral

peritoneum: all non-retroperitoneal digestive organs

Retroperitoneal organs

are not covered or not completely covered by

peritoneum: esophagus, pancreas, last part of duodenum, ascending

and descending colon, rectum

Greater Omentum

Apron like structure that is superficial to the small intestine and transverse colon and is a site of fat deposition, occurs to people who are overweigh

Lesser omentum

Suspends the stomach from the inferior boarder of the liver and provides a pathway connecting to liver

Mesentery Proper

A vertical strap tissue that is anterior to vertebrae lumbar and anchors to all small intestine expect initial portion (duodenum)

Mesocolon

Attaches to two portions of the large intestine (transverse and sigmoid colon) to the posterior abdominal wall

Mucosa

Contains fenestrated capillaries and lymphatic capillaries called lacteals.

What is Mucosa made of?

Epithelium that lines the lumen; contains goblet cells; subtype changes

through GI tract

Lamina propria: areolar connective tissue containing MALT

Muscularis mucosae: thin layer of muscle that creates folds in stomach and

small intestine to increase surface area

Submucosa

Contains mucin-secreting glands to help with peristalsis, blood and lymph vessels, nerves. Made by areolar or dense irregular connective tissue.

Muscularis

Is made by two layers of smooth muscle tissue: a inner circular layer and an outer longitudinal layer. Thickening of inner layer forms sphincters that open or close a passageway. Myenteric nerve plexus originates from vagus nerve and controls contractions.

Serosa or Adventitia

Serosa (for intraperitoneal organs, also called visceral peritoneum) or Adventitia (for retroperitoneal organs) is made by areolar connective tissue.