16.1 - Intro

primary function of the digestive system

transfer nutrients, water, and electrolytes form ingested food into the body’s internal environment

the four digestive processes are

motility, secretion, digestion, and absorption

what is motility

muscular contractions that mix and move forward the contents of the digestive tract

the two types of digestive motility are ___ and ___

propulsive movements, mixing movements

propulsive movements are

movements that push forward contents through the tract

the functions of mixing movements include

the digestion of food by mixing food with digestive juices and facilitating absorption by exposing all parts of internal contents to absorbing surfaces of digestive tract

secretions are made up of

water, electrolytes, and specific organic constituents

what instigates the release of secretions?

neural or hormonal stimulation

what happens to secretions after serving their purpose in digestion?

reabsorbed into the blood (unless vomiting or diarrhea)

what is digestion

the biochemical breakdown of structurally complex foodstuffs into smaller, absorbable units

digestion is accomplished via means of

enzymatic hydrolysis

digestion of carbs?

carbs —> monosaccharides

digestion of proteins

proteins —> amino acids

digestion of fats?

triglycerides —> glycerol and 2 fatty acids

absorption

the transfer from the digestive tract lumen into the blood or lymph of small units resulting from digestion, water, vitamins, and electrolytes

the digestive tract is made of

mouth, throat, esophagus, liver, pancreas, small intestine, and rectum

the accessory digestive organs are

salivary glands, exocrine pancreas, biliary system

the biliary system is made of

gallbladder and liver

what are the layers of teh digestive tract wall

mucosa, submucosa, muscularis externa, serosa

where in the digestive wall is the mucosa

the luminal surface of the digestive tract

what does the mucosa look like, structurally

highly folded surface area

what role does the structure of the mucosa play in its function

increases surface area for absorption

what are the layers of the mucosa

mucous membrane, lamina propria, muscularis mucosa

what is the function of the mucous membrane

protective layer

feature of the mucous membrane

modified in certain areas for secretion and absorption

what is the makeup of the mucous membrane?

endocrine gland cells, exocrine gland cells, specialized epithelial cells

what does the lamina propria consist of

gut-associated-lymphoid tissue (GALT)

what is the function of the lamina propria

defence against disease-causing intestinal bacteria

what is the muscularis mucosa made of

sparse layer of smooth. muscle

what does the muscularis mucosa do

changes the folding pattern of the mucosal surface

what is the submucosa made of

thick layer of connective tissue

what does the submucosa do

provides the digestive tract with distensibility and elasticity

what does the submucosa contain

larger blood and lymph vessels and the submucosal plexus

what is the muscularis externa made of

smooth muscle

what are the two layers of the muscularis externa

circular layer and longitudinal layers

the circular layer is the ___ layer

inner

the longitudinal layer is the ___ layer

outer layer

contraction of the circular layer ___

decreases diameter of lumen

contraction of the longitudinal layer ____

shortens the tube

function of the muscularis externa

contraction produces propulsive and mixing movements

what does the muscularis externa contain

myenteric plexus

where is the myenteric plexus located

between the two muscle layers

what does the serosa do

secretes serous fluid

what does serous fluid do

lubricates and prevents friction between digestive organs and surrounding viscera

the serosa is continuous with

the serosa

what does the mesentary do

provides relative fixation and supports digestive organs in proper place while allowing them freedom for mixing and propulsive movements

how is digestive function regulated

autonomous smooth muscle function, intrinsic nerve plexuses, extrinsic nerves, gastrointestinal hormones

what is autonomous smooth muscle function

self induced electrical activity: slow-wave potentials; basic electrical rhythm (BER)

what causes the (BER)

the cells of cajal

describe the cells of cajal

muscle-like but non contractile

where are the cells of cajal located

interstitial

intrinsic nerve plexuses consists of

submucosal plexus and myenteric plexus

the enteric nerve plexuses is the collective name for the

intrinsic nerve plexuses