Anatomy and Physiology II- Exam II

GI Tract (alimentary canal)

Continuous tube from mouth to anus that facilitates digestion and absorption of food and nutrients

Accessory digestive organs

Organs that assist in digestion but not part of GI tract. Help with mechanical digestion (chewing) and/or chemical digestion (enzymes, bile, etc)

Salivary glands

Secrete saliva into GI tract which chemically breaks down food on a small scale

Main functions of digestive systems

Ingestion, Motility, Secretion, Digestion, Absorption, Elimination

Mucosa (GI Tract Wall)

Innermost layer of GI tract wall that directly faces lumen that shields the body from home

Submucosa

Connective tissue layer of the GI tract wall containing larger blood vessels, lymphatic vessels and nerves

Muscularis Externa

Responsible for mixing and propulsion in GI tract wall; comprised of two muscular layers that produce motility using peristalsis and sphincters

Serosa/adventitia

Outermost layer of GI tract wall that provides covering and support. Serosa reduces friction and adventitia anchors portions of GI tract to surrounding structures

Enteric nervous system role in digestion system

Network of neurons within GI tract wall that detects changes within the GI tract wall and coordinates changes

Autonomic nervous system role in the digestive system

Parasympathetic- rest and digest; relaxes many sphincters open

Sympathetic- fight or flight; contracts many sphincters close

Peritoneum

Serous membrane that lines abdominopelvic cavity

Mesentary

anchor the intestines to the posterior abdominal wall while supplying them with blood, lymphatics, and nerves

Mucosa associated lymphatic tissue MALT

acts as a primary defense system that monitors and fights germs entering through the body's mucous membranes

Upper GI Tract Organs

Oral Cavity and salivary glands, pharynx, esophagus, stomach, duodenum

Bolus

Food + saliva

Pharynx

Bolus enters during swallowing, assisted by saliva and mucus which lubricate

Esophagus

Transports bolus from pharynx to stomach via peristalsis

Regions of the oral cavity

Vestibule (where zyn goes) and oral cavity proper (where food goes)

Palate

Roof of oral cavity that elevates during swallowing to close nasopharynx

Pharynx

Muscular pathway shared by respiratory and digestive systems

Directs food from oral cavity to esophagus

What kind of cells do the oropharynx and laryngopharynx have and why

Nonkeratinized stratified squamous to protect against friction

Esophagus

Muscular tube that takes bolus to the stomach via peristalsis, closes when empty

Upper (superior) esophageal sphincter

Located between pharynx and esophagus, normally closed and prevents air from entering esophagus while breathing- relaxes during swallowing

Lower (inferior) esophageal sphincter

Located between esophagus and stomach, relaxes as bolus approaches stomach and closes after to limit gas reflux

Swallowing phases

Oral phase (voluntary) which involves chewing

Pharyngeal phase (involuntary) where soft plate elevates to close nasopharynx

Swallowing apnea

Breathing temporarily stops during breathing

Four regions of the stomach

Cardia, Fundus, Body, Pylorus

Rugae

Gastric folds of the stomach mucosa that allows that stomach to stretch

Cells that line the stomach

Simple Columnar epithelium cells that are exposed to a high acidic environment that are replaced rapidly

Surface mucous cells

secretes alkaline mucin

Mucous neck cell

secretes a much less alkaline mucin

Parietal Cells

secrete intrinsic factor (important for B12 absorption) and hydrochloric acid to create stomachs acidic environment (H+ and Cl- are secreted separately)

Chief Cells

secrete pepsinogen, inactive precursor of pepsin to be later activated in stomach by HCl

Pepsin role

Digests protein to smaller pepsides

G-cells

Endocrine cells that secrete gastrin (hormone) into the blood for increased gastric secretion and motility

Cephalic phase of stomach activity

Brain knows food is coming and stomach gets ready

Gastric phase of stomach activity

Food arrives to stomach, stomach expands, neural reflexes, increased secretion and concentration

Intestinal phase

Small intestine sends signal to slow down; decreased motility and secretion and gastric emptying is slowed

Small intestine

Organ in GI tract responsible for completing chemical digestion and most absorption

Duodenum

First part of small intestine that connects to the stomach that is a major site for continuing chemical digestion. Acts as a mixing chamber and receives chyme and bile + pancreatic juices to assist

Jejunum

Longest portion of small intestine which is the primary absorber

Circular folds

“Speed bumps” in the jejunum that cause friction to slow food down

Villi

Structure in the jejunum that increase absorption and surface activity and contain blood capillaries (absorb water soluble nutrients) and lymphatic capillaries (absorb fat soluble nutrients)

Microvilli

Brush like projections in villi that contain enzymes to assist chemical digestion

Ileum

Last region of the small intestine that is crucial in vitamin B12 absorption via intrinsic factor released by parietal cells

Biliary Apparatus

Network of ducts that transport bile from the liver to gallbladder to the duodenum

Pancreatic ducts

Main and accessory (backup)

Hepatic portal system

takes blood from GI tract to liver

Bile

Yellow green fluid containing bile salts, bicarbonate, cholesterol, pigments, and water

Bile emulsification

Bile salts digest lipids mechanically

Gallbladder

stores bile, not a gland as it doesn’t produce

Pancreas

Organ that breaks everything down. Endocrine functions through hormones and exocrine functions through pancreatic juice which contains digestive enzymes

Large intestine

Absorbs remaining water and electrolytes and compacts and stores fecal material

Cecum

First portion of large intestine