Final Exam

digestion

process by which food substances are changed into forms that can be absorbed through cell membranes by chemical and mechanical means

ingestion

taking food into the mouth

movement of food

the passage of food along the GI tract

absorption

the passage of digested food from GI tract into bloodstream for distribution to cells

defecation

the elimination of undigested material from the GI tract

alimentary canal (GI tract)

extends from mouth to anus
includes:
mouth, pharynx, esophagus, stomach, small and large intestine

accessory organs

release secretions into the alimentary canal that help digest food
include: salivary glands, liver, gallbladder, pancreas

mucosa

innermost layer of alimentary canal
composed of epithelium and CT
epithelium extends into lumen
glands secrete mucus

submucosa

beneath mucosa
nourishes mucosa
carry absorbed nutrients away

muscularis

two layers of muscle
circular muscle around submucosa
longitudinal layer around circular muscle
moves food through canal with mixing and peristalsis

serosa

outermost layer
visceral peritoneum
aids in lubrication

mesentery

intestinal peritoneal extensions

mixing

mechanical digestion
food + digestive juices + mucus
circular muscular layer

peristalsis

accomplished by movement of longitudinal muscle layer

sphincter

a strong circular muscle which prevents regurgitation of food

gastroesophageal sphincter

between esophagus and stomach

pyloric sphincter

between stomach and small intestine

ileocecal valve

between small and large intestine

internal and external anal sphincter

between large intestine and outside

parasympathetics

activates digestion

sympathetic

slows digestion

submucosal plexus

controls secretions

myenteric plexus

controls peristalsis

mouth

referred as oral or buccal cavity
adapted to receive food and start mechanical and chemical digestion by chewing and mixing food with saliva

salivary glands

secrete saliva
binds food together and begins chemical digestion of polysaccharides
major types:
parotid, submandibular, sublingual

pharynx

throat
passageway of food and air into esophagus

esophagus

passageway for food from pharynx to stomach
located in mediastinum behind trachea and goes through diaphragm at esophageal hiatus
has many mucous glands

esophageal hiatus

herniation of the cardiac region of the stomach through a weakened esophageal hiatus resulting in esophageal tissue being exposed to gastric juices

stomach

referred as gastric
functions to mix bolus into chyme and begin the chemical breakdown of proteins

pyloric sphincter muscle

lies between pylorus and duodenum

rugae

mucosal folds in stomach
formed by gastric villi which then forms
gastric pits which are between the villi

gastric glands

located along gastric pits

gastric juice

secreted by gastric glands
composed of mucus, pepsin, HCL, intrinsic factor, gastrin

mucus

function is lubrication, protection of mucosa from digestion

pepsin

function is protein digestion into peptides

HCL

function is to denature proteins, and kill microbes in food

intrinsic factor

functions in aiding absorption of Vitamin B12 for erythropoiesis

gastrin

regulatory hormone

mucous cells

secrete mucus

chief cells

secrete pepsin

parietal cells

secrete HCL and intrinsic factor

g cells

secrete gastrin

pancreas

endocrine cells produce hormones glucagon and insulin
most cells make up pancreatic acini which makes pancreatic juice
secretes pancreatic juice into pancreatic duct that leads to small intestine

liver

referred as hepatic
digestive function is emulsification of fats

hepatic lobules

functional unit of liver
contains hepatocytes which provide most functions
contains Kupffer's cells (macrophages)

Kupffer's cells

remove and destroy:
microbes, foreign matter, worn platelets and erythrocytes

liver functions

filter blood and production/secretion of bile

hepatic artery

supplies oxygenated blood to liver

hepatic portal vein

supplies deoxygenated blood to liver filled with:
newly absorbed nutrients from small intestine
toxins from stomach
worn blood cells from spleen

hepatic vein

blood leaving liver cells drain into central veins that come together to form

bile

composed of bile salts (digestive function)
bile pigments(biliverdin and bilirubin)
cholesterol
electrolytes

gallbladder

store bile between meals
flows by 2 routes
liver that goes to common hepatic duct
gallbladder to cystic duct
that forms common bile duct

hepatopancreatic spincter muscle

keeps the common bile duct closed

emulsification

breaking up of fat globules into small droplets to increase surface area

small intestine

major site of chemical digestion (duodenum)
major site of absorption of nutrients

duodenum

nearest part of the stomach

jejunum

mid region

ileum

near large intestine

monosaccharides

carried away by submucosal blood capillaries

amino acids

carried away by blood capillaries

fatty acids

chylomicrons are absorbed by lacteals (lymphatic capillaries) into the lymphatic system

large intestine

contains cecum, colon, rectum, and anal canal
divided into ascending, transverse, descending, and sigmoid colon
lacks villi

intestinal flora

bacteria that digest substances humans can't digest

feces

undigested and unabsorbed material

sensory receptors

sensitive to environmental changes and initiate impulses to the brain and spinal cord

general (somatic) senses

receptors associated with skin, muscles, joints, and viscera

special senses

located in large complex organs in the head
(vision, hearing, equilibrium, taste, smell)

olfactory receptors

chemoreceptors that are located in the upper nasal cavity
chemicals must be dissolved in solution to be detected

gustation

sense of taste

taste receptors

chemoreceptors that are located in taste buds
chemicals must be dissolved in saliva to be detected

auricle

outer ear

external acoustic (auditory) meatus

ear canal

auditory (eustachian) tube

passageway which connects middle ear to nasopharynx
functions to equalize pressure on both sides of tympanic membrane

cochlea

snail shaped portion

semi circular canals

three rings

vestibule

area between cochlea and semi circular canals

mechanoreceptors

responsible for the sense of hearing are contained in spiral organ (organ of corti)

static equilibrium

functions to sense the position of the head and help us maintain posture while motionless

macula

organ of static equilibrium
composed of hair cells
when the head is moved, the hair cells bend

dynamic equilibrium

functions to prevent loss of balance during rapid head or body movement

vision

organ is the retina of the eye
sensory receptors are called photoreceptors

outer tunic

fibrous and functions for protection
contains cornea and sclera

cornea

transparent anterior portion
helps focus 75% incoming light rays

sclera

white posterior portion
functions for protection and attachment of eye muscles

middle tunic

vascular and contains:
choroid coat, ciliary body, ciliary muscles, iris

choroid coat

membrane joined loosely to sclera containing many blood vessels to nourish the tissues of the eye

ciliary body

anterior extension from choroid coat

ciliary muscles

control the shape of the lens

accommodation

process by which the lens changes shape to focus on close objects

iris

colored ring around pupil

inner tunic

nervous, sensory
contains retina

retina

inner lining of eyeball site of photoreceptors

pathway of light

cornea
aqueous humor
lens
vitreous humor
photoreceptors in retina

cones

photoreceptors for color vision produce sharp images

rods

photoreceptors for night vision produce silhouettes of images

visual nerve pathway

photoreceptors of retina (cones/rods)
optic nerve (CN II)
thalamus
primary visual cortex

from the pharynx to the anus

Peristalsis occurs in the digestive tract

moistening, binding, and dissolving food particles; beginning chemical digestion of carbohydrates; and cleansing the teeth and mouth.

The functions of saliva include

protein and fat in the small intestine

Secretion of cholecystokinin from the intestinal wall is stimulated by

cholecystokinin

Pancreatic digestive secretions are regulated by