University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2019
Views:

187

Pages:

11
Author:

46280dk

The Digestive System Chapter 25 • Digestive functions and processes • Anatomy of the Digestive System – Mouth, Pharynx, Esophagus – Gastrointestinal Tract • • • • • • Stomach Liver, Gallbladder, Pancreas Small Intestine Large Intestine (colon) Rectum Anus Digestive System Functions • Ingestion = intake of food • Digestion = breakdown of complex nutrient molecules into simple nutrient molecules • Absorption = uptake of nutrients into the blood and lymph • Defecation = elimination of undigested material Stages of Digestion 1. Mechanical Digestion is the physical breakdown of food into smaller particles by: – chewing with teeth – churning with stomach and intestines 2. Chemical Digestion is series of hydrolysis reactions by acid (from the stomach) and enzymes (from saliva, stomach, pancreas, intestines) that break down nutrient macromolecules into their monomers: – polysaccharides  monosaccharides – proteins (polypeptides)  amino acids – fats  glycerol and fatty acids Anatomy of the Digestive System • Digestive tract – 30 foot long tube extending from mouth to anus • Accessory organs – teeth, tongue, salivary glands – liver and gallbladder – pancreas The Tongue, Pharynx and Larynx Pharynx The Tongue • Dorsal surface is covered by a keratinized stratified squamous epithelium with numerous specialized papillae: – Circumvallate Papillae – Foliate Papillae – Fungiform Papillae – Filiform Papillae • Circumvallate, Foliate and Fungiform papillae have taste buds. Filiform do not. • Lingual Tonsil(s) contains lymphatic tissue in the root of the tongue • Foramen Cecum is a shallow pouch that is a remnant of where the thyroid gland formed from the embryonic pharynx Tongue Papillae •Circumvallate: 8-12 large, domed papillae arranged in a “V” •Foliate: low parallel ridges on the lateral edge of tongue •Fungiform: mushroom-shaped papillae that look like small spots •Filiform: smallest and most numerous papillae. Conical shape with highly keratinized epithelium and no taste buds. Filiform Papillae Filiform Papillae are covered with a keratinized stratified squamous epithelium. They are distributed over the entire anterior surface of the tongue. The stiff tips of the papillae help grip food and since they point backward they help move food towards the pharynx for swallowing. Circumvallate (vallate) Papillae Circumvallate papillae are covered with a slightly keratinized statified squamous epithelium. Taste buds are embedded in the epithelium around the papilla. Serous glands (von Ebner’s glands) surround the papillae and release a watery secretion that clears the cleft so the taste buds can respond to new gustatory stimuli. Taste Buds • Taste buds are clusters of 50-100 columnar cells in the tongue epithelium. The taste pore is the opening of the taste bud. • Taste cells have microvilli called “taste hairs” with specific types of taste receptors. • Taste cells synapse with sensory nerve fibers at their base • Basal cells are stem cells that continually replace the sensory and supporting cells. • Taste buds are also found on the soft palate, epiglottis, and the pharynx. Taste Pore and Taste Hairs of a Taste Bud