Digestive System

Alimentary canal (GI Tract)

tube from mouth to anus

Accessory Structures

structures that aid alimentary canal with digestion

Functions of digestive system

indigestion, digestion, absorption, defecation

Indigestion

putting something into the alimentary canal

Digestion

breaking ingested material into smaller components, mechanical and chemical

Absorption

movement of nutrients from GI tract to blood (carbs, proteins, lipids, vitamins, minerals)

Defecation

getting rid of unabsorbable material

Soft palate

uvula, lined by stratified squamous

Tongue

manipulates ingested material, taste, speech

Oral cavity

site of ingestion and mechanical and chemical digestion

Incisors

used for biting and clipping

Canines

used for puncturing and tearing

Premolars and Molars

used for grinding and pulverizing

Crown

visible tooth structure

Tooth Root

within the alveolus

Pulp Cavity

contains blood vessels, nerves and living cells

Enamel

hard external layer of crown

Dentin

hard layer, deep to enamel

Salivary glands

parotid, sublingual, submandibular, saliva

Saliva

99% water, mucus, enzymes, antibodies, salivary amylase

Deglutition

act of swallowing

Deglutition 1

tongue pushes the bolus to the back of the pharynx

Deglutition 2

larynx pushes up and the epiglottis closes over the glottis

Deglutition 3

the bolus moves to the esophagus

Deglutition 4

esophageal muscles move the bolus towards the stomach through peristaltic contractions, bolus enters the stomach now called chyme

Lumen

opening within a hallow organ

Mucosa

secretion and absorption, simple columnar or stratified squamous

Submucosa

CT, blood and lymphatic vessels

Muscularis

layers of smooth muscle

Peristalses

rhythmic contraction for propulsion

Segmentation

mixing (mechanical digestion)

Stomach anatomy

cardiac sphincter, body, pylorus, pyloric sphincter, rugae

Stomach Function

acid production, storage, intrinsic factor

Gastric Pits

invagination of stomach wall

Gastric Glands

secretory cells

Mucous cells

alkaline mucous

Parietal Cells

hydrochloric acid and intrinsic factor

Intrinsic factor

allows small intestines to absorb b12, b12 needed for RBC production and DNA/nerve function

Gastrin

endocrine cell, increases stomach secretions and motility

Pepsinogen

a chief cell, digests proteins, activates the stomach to become pepsin

Duodenum

first -12in of small intestine, receives secretions from stomach, liver, pancreas and gallbladder

Jejunum

-7ft of small intestine, majority of digestion and absorption

Ileum

-9ft of small intestine, minority of digestion and absorption, joins large intestine at the cecum

Intestinal Villi

increases surface area, contains blood and lymphatic capillaries

Liver

produces bile and stores nutrients

Bile

mechanically digests lipids

Gallbladder

stores and concentrates bile

Pancreas

secretes digestive enzymes for carbs, lipids and proteins

Large intestine

absorbs water and compacts chyme into feces, contains microbiome, mucous secreting goblet cells

Internal Anal Sphincter

smooth muscle

External anal sphincter

skeletal muscle

Mass movement

strong, regular propulsion

Serosa

ct tissue

Small intestines

long tube that connects stomach to large intestine, majority of digestion and absorption

Stomach