BIOL 1051 Lecture Notes - Muscular Layer, Muscularis Mucosae, Peritoneum
Week 12: Digestive System I (Overview)
Major organs; mouth, pharynx, oesophagus, stomach, small intestine, large intestine
Accessory organs; teeth, tongue, salivary glands, liver, gallbladder, pancreas
Digestive tract;
➢ Continuous tube extending from mouth → anus
➢ Muscular tube
➢ Internal surfaces exposed to external environment
Major functions;
➢ Supply the body with nutrients, organic molecules, electrolytes, water
➢ Gastrointestinal tract (GIT) optimises conditions for digestion/absorption
➢ Breaks down ingested food into substrates for cells
Functions of the digestive system;
1. Ingestion
o Material enters digestive tract via mouth
2. Mechanical processing
o Chewing
o Easier to propel along tract
o Increases surface area to allow easier breakdown
3. Digestion
o Chemical breakdown of food for absorption
o Large molecules (e.g. carbohydrates/starches) broken down into small molecules (e.g.
absorbable sugars, lipids)
4. Secretion
o Release of water, acids, enzymes, buffers, salts
5. Absorption
o Movement of substrates, electrolytes, vitamins and water across epithelium into interstitial
fluid
6. Excretion
o Removal of waste products from body
Organisational structure (consistent of every organ)
4 layers;
➢ Mucosa
o Mucous membrane
o Secretion/absorption
➢ Submucosa
o Binds mucosa to muscularis
externa
➢ Muscularis externa
o Smooth muscle
➢ Serosa (visceral peritoneum)
o Membrane that attaches
organs to cavity walls
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Document Summary
Major organs; mouth, pharynx, oesophagus, stomach, small intestine, large intestine. Accessory organs; teeth, tongue, salivary glands, liver, gallbladder, pancreas. Continuous tube extending from mouth anus. Supply the body with nutrients, organic molecules, electrolytes, water. Gastrointestinal tract (git) optimises conditions for digestion/absorption. Breaks down ingested food into substrates for cells. Functions of the digestive system: ingestion, material enters digestive tract via mouth, mechanical processing, chewing, easier to propel along tract. Submucosa: binds mucosa to muscularis externa. Serosa (visceral peritoneum: membrane that attaches organs to cavity walls. Inner lining: mucous membrane makes up digestive epithelium. Lamina propia: areolar tissue containing, blood and lymphatic vessels, sensory nerve endings, lymphoid tissue, muscularis mucosae (thin smooth muscle layer) Submucosa: dense, irregular connective tissue, surrounds muscularis mucosae, large blood vessels and lymphatic vessels, may contain exocrine glands, secrete buffers (help regulate ph) and enzymes into digestive tract. Muscularis externa: smooth muscle cells (two layers)