PART 1 of the Digestive system - mouth, pharynx, esophagus and stomach - Anatomy and Physiology 2

Digestive system

The mechanical and chemical breakdown of food so nutrients can be absorbed and used by cells

Mechanical digestion

Physical breakdown of food, such as chewing

Chemical digestion

Breakdown of food using enzymes and acids

Alimentary canal

Muscular tube from mouth to anus through which food passes

Accessory organs

Organs like liver and pancreas that aid digestion but food does not pass through them

Layers of the alimentary canal

Mucosa, submucosa, muscular layer, serosa

Mucosa

Innermost layer in contact with food, involved in secretion and absorption

Lumen

The hollow space inside the alimentary canal through which food moves

Submucosa

Layer containing blood vessels, lymphatic vessels, and nerves

Muscular layer

Has circular and longitudinal smooth muscle for movement

Circular muscle

Wraps around the alimentary canal, contracts to narrow it

Longitudinal muscle

Runs lengthwise, contracts to shorten the canal

Serosa

Outermost layer, secretes fluid to reduce friction between organs

Mesentery

Connective tissue that holds intestines in place and contains blood supply

Villi

Fingerlike projections in the small intestine that increase surface area for absorption

Microvilli

Tiny projections on villi that further increase surface area

Goblet cells

Produce mucus to protect the mucosa

Mixing movement

Rhythmic contractions that mix food with digestive enzymes

Peristalsis

Wave

Mouth

First part of the digestive tract, begins mechanical digestion by chewing

Oral cavity

Chamber between palate and tongue

Vestibule

Space between teeth, lips, and cheeks

Tongue

Muscular organ with taste buds, helps move food and aids swallowing

Lingual frenulum

Connects tongue to floor of the mouth

Papillae

Projections on tongue that contain taste buds and help with friction

Lingual tonsils

Lymphatic tissue at root of tongue

Palate

Roof of mouth; hard (anterior) and soft (posterior) portions

Uvula

Dangling structure from soft palate that blocks nasal passage during swallowing

Palatine tonsils

Lymphatic tissue near the uvula

Pharyngeal tonsils (adenoids)

Lymph tissue at back of nasal cavity

Teeth

Break food into smaller pieces, aiding in mechanical digestion

Primary teeth

First set of 20 teeth that are replaced by permanent ones

Secondary teeth

Adult set of 32 permanent teeth

Tooth structure

Consists of crown, root, enamel, dentin, pulp, and cementum

Salivary glands

Produce saliva to moisten food and begin carbohydrate digestion

Saliva

Contains water, mucus, and salivary amylase for starch digestion

Parotid gland

Secretes watery, enzyme

Submandibular gland

Secretes mixed watery and mucus saliva; located under jaw

Sublingual gland

Secretes thick, mucus

Pharynx

Connects nasal and oral cavities to larynx and esophagus

Three parts of pharynx

Nasopharynx, oropharynx, laryngopharynx

Swallowing

Voluntary and reflexive process that moves food from mouth to esophagus

Esophagus

Collapsible tube that transports food to the stomach

Lower esophageal sphincter

Prevents stomach contents from re

Stomach

J

Rugae

Folds in the stomach that allow for expansion

Stomach regions

Cardia, fundus, body, pylorus

Pyloric sphincter

Controls food release from stomach to small intestine

Gastric pits

Openings in stomach lining that lead to gastric glands

Mucous cells

Secrete mucus to protect stomach lining

Chief cells

Secrete pepsinogen, which becomes pepsin to digest proteins

Parietal cells

Secrete hydrochloric acid to activate pepsinogen

Intrinsic factor

Secreted by stomach, needed for vitamin B12 absorption

Gastric juice

Combination of mucus, pepsinogen, and hydrochloric acid

Gastrin

Hormone that stimulates secretion of gastric juice

Cholecystokinin (CCK)

Hormone released from intestine to slow stomach activity

Chyme

Semi

Stomach absorption

Absorbs small amounts of water, alcohol, salts, and drugs

Emptying rate

Fats delay stomach emptying; carbs empty faster

Gastric bypass

Surgery to reduce stomach size, limits food intake

Pernicious anemia

Caused by lack of intrinsic factor leading to B12 deficiency