anatomy and physiology digestive system

what is the GI tract

a continuous tube from the mouth to the anus that supports digestion, absorption, nutrient regulation and elimination

what are the 4 major digestive functions

mechanical and chemical digestion, secretion, absorption, and motility (movement)

what is mastication

chewing food into smaller pieces

how many teeth do adults have

typically 32, incisors, canines, premolars, and molars

which tongue papillae do not contain taste buds

filiform papillae; they are the most numerous and serve a mechanical role

what is fungiform papillae

mushroom-shaped papillae, especially near the tip of the tongue, involved in distnguishing tastes

what are circumvallate papillae

large, dome-shaped papillae in rows toward the back of the tongue; they contain taste buds

what does salivary amylase beigain digesting

carbohydrates

name the 3 major salivary glands

parotid, sublingual, and submandibular

what does the parotid gland secrete

salivary amylase, whcih begians carbohydrate digestion, it contributes much of the saliva when stimulated

what is a feature of the sublingual gland

it is the smallest salivary gland and produces about 10% of salivary volume

what does the submandobular gland secrete

serous and mucous fluid

what is the function of the esophagus

a muscular tube connecting the laryngopharynx to the stomach; it moves food by peristalsis

what does the upper esophageal sphincter do

helps keep food from entering the trachea

what does the lower esophaeal sphincter do

helps prevent stomach contents from refluxing upward

what are the 4 tunics of the digestive tract

mucosa, submucosa, muscularis, and serosa/adcentitia

what is the mucosa

the innermost lining of the kumen; includes mucosus epithelium, lamina propria, and muscularis mucosa

what is found in the submucosa

connective tissue, submucosal plexus, blood vessels, and small glands

what does the myenteric plexus help control

peristaltic contractions; it lines between the circulation and longitudinal muscle layers

what is peristalsis

wave-like muscular contractions that move contents through the digestive tract

what are gastric ulcers

erosions where the GI mucosal membrane breaks down and is replaced with scar tissue

what causes gastric ulcers according to the slids

pissible causes include: NSAIDs such as aspirin, highly acidic foods/ liquids, and chronic stress

where is the stomach located

in the left upper quadrent of the abdomen

what are the main functions of the stomach

stores food and gases and mixes food with secretions to form liquid chyme

what are the 4 regions of the stomach

cardia, fundus, body, and pyloric region

what are rugae

folds of the stomach mucosa and submucosa that forms when the stomach is empty

what are the 3 muscle layers of the stomach

circular, longitudinal, and oblique smooth muscle

what is the approximate pH of the stomach

about pH 2

what is the cardia

the opening from the esophagus into the stomach; it contains the cardio-esophageal sphincter

what is the fundus

the most superior stomach region; it allows gas to acumulate and can store undigested food briefly

what is the body of the stomach

the largest stomach region; it has greater and lesser curvatures

what is the pyloric region

the opening from the stomach into the small intestine; its sphincter regulates chyme passage

what do goblet cells secrete

mucin, which lubricates food and helps protect the stomach

what do parietal cells secrete

hydrochloric acid (HCl) and intrinsic factor

what does HCl do in the stomach

denatures proteins, kills bacteria, and activates pepsin

what is intrinsic factor needed for

vitamin B12 absorption in the small intestine

what do chief cells secrete

pepsinogen, whcih is converted to pepsin in the presence of HCl

what does pepsin do

help break down proteins

what do G cells secrete

gastrin, a hormone that stimulates HCl release

what does the greater omentum connect/support

the stomach and transverse colon

what does the lesser omentum connect/support

the stomach, duodenum, and liver

what is the mesentery proper

a fan-shaped peritoneal fold suspending the jejunum and ileum; it contaions blood vessels, lymph vessels, and nerves

what are the 3 parts of the small intestine

duodenum, jejunum, and ileum

what are the main functions of the small intesine

digestion is completed and most nutrient absorption occurs there

what enters the duodenum

chyme from the stomach, bile from the live/gallbladder, and pancreatic products

whcih hormones are released by the duodenum in the slides

secretion and cholecystokinin (cck)

what is the approximate pH of the duodenum

7, an alkaline environment

what structures increase small intestinal surface area

circular folds (plicae circulares), villi, and microvilli

what are circular folds

deep mucosal and submucosal folds that slow chyme movement and allow more absorption

what are villi

fingerlike ectensions of the mucosa that increase surface area

what is a lacteal

a lymphatic capillary inside a villus that absorbs lipids and fat-soluble vitamins

what are microvilli

prohections from intestinal cell membrains that form the brush border and release enzymes

what are intestinal glands

pits in the mucosa between villi

what are important function of the ileum

contains peyer’s patches, absorbes vitamin B12, reabsorbs bile salts in its terminal portion, and joins the larger intestine at the ileocecal valve

what are peyer’s patches

lymphatic tissue in the ileum that helps protect the intestinal tract from microorganisma

what is the cecum

the proximal end of the large intestine that receives contents from the ileum; the appendix attaches to it

name the major sections of the colon

cecum, ascending, transverse, decending, and sigmoid colon

what are haustra

pouch-like sections of the colon

what are taeniae coli

bands of muscle in the colon that contracts to helpmove feces

what are the main funcations of the large intestine

converts chyme into feces, absorbs water and salts, secreats mucus, supports bacterial vitamin synthesis, and moves waste

what do bacteria in the large intestine do

ferment indigestible carbohydrates, produce gases, synthesize B-complex vitamins and vitamin K, and colonize the colon

what is the difference between the anal sphincters

the internal sphincter is involentary, the external sphincter is under voluntary control

where is the pancreas located

posterior to the stomach

why is the pancreas called a mixed gland

it has exocrine digestive secretions and endocrine hormine secretions

which hormones does the pancrease release

insuline and glucagon

what does pancreatic bicarbonate do

neutralizes acidic chyme entering the duodenum

what does pancreatic lipase digest

fats, after emulsification

what does pancreatic amylase digest

starches/polysaccharides

what do trypsin and chymotrypsin digest

proteins and peptides

what supplies oxygenated blood to the liver

the hepatic artery

what does the hepatic portal vein carry

venous blood from the digestive tract to the liver

where do hepatic veins drain

into the inferior vena cava

list major liver functions

Stores glucose as glycogen; makes glucose from non-carbohydrates; stores vitamins/minerals; processes nutrients; detoxifies substances; makes plasma proteins and clotting factors; produces bile; and excretes bilirubin and other substances

what does the gallbladder do

stores and concentrates bile between meals and releases it into the duodenum

what simulates gallbladder contraction

cholecystokinin (CCK)

what does the cystic duct do

transports bile to and from the gallbladder

what does the common bile duct do

transports bile to the small intestine

what triggers the salivation reflex

sight, smell, taste, or chwing of food; parasympathetic stimulation activates salivary glands

what are the 3 phases of swallowing

voluntary, phartngeal, and esophageal phase

what happens dueing the pharyngeal phase of swallowing

The soft palate closes the nasopharynx, muscles contract, the esophageal sphincter relaxes, and the epiglottis tilts while vocal folds close to protect the airway.

what happends during the esophageal phase

peristalic waves move food toward the stomach; gravity may assist

what does ghrelin do

it is released from the stomach and increases feelings of hunger

what does leptin do

it is produced by fat cells and decreases fellings of hunger, it helps regulate long-term energy use

what happens during the cephalic phase of digestion

sight, smell, taste, or thought of food triggers vagal impulses that simulate stomach secretions

what initiates the gastric phase

stomach distention and the presence of nutrients; this stimulates gastric secretions and segmentaion

what happens during the gastrointestinal phase

Acidic chyme enters the duodenum, stimulating secretin and CCK; these regulate pancreatic and gallbladder secretions and inhibit gastric motility

what does secretion do

It responds to acidic chyme and stimulates pancreatic bicarbonate delivery; it also inhibits gastric motility and enzyme secretions.

what does CCK do

stimulates pancreatic enzyme release, gallblader contraction, and relacation of the major papilla

what is emesis

forceful ecpulsion of stomach contents throught the mouth and sometimes nose

what are the 2 phases of vomiting

Retching: abdominal and diaphragm contractions increase pressure

Expulsion: the upper esophageal sphincter relaxes and contents are expelled

how long do mass movements take to move feces

about 8-12 hours, offten follow a meal

what is the gastricolic reflex

A reflex stimulated by stomach and rectal wall distention that increases colon contractions and helps initiate defecation

which anal sphincter is viluntatily controlled

the external anal sphincter

where does carbohydrate digestion begin and finish

It begins in the mouth and is completed in the duodenum/small intestine

Where does protein digestion begin and finish

It begins in the stomach and is completed in the duodenum/small intestine

Where does fat digestion begin

In the duodenum/small intestine

What is hydrolysis

Breaking a molecule into smaller molecules by adding wate

What does maltase do

Breaks maltose into two glucose molecules

What does sucrase do

Breaks sucrose into glucose and fructose

What does lactase do

Breaks lactose into glucose and galactose