Digestive System

2 parts

GI Tract- tublar structure from mouth to anus

Accessory structures- Teeth, tongue, Salivary glands, liver, gallbladder, and pancreas, found within tract

1. Ingestion- eating, drinkin, consume food

2. Secretion- saliva, enzymes

3. Propulsion- move food along (smooth muscle)

4. Digestion (Catabolism)- breakdown of food

                    A. Mechanical- no enzymes

                    1. Chewing, mixing with tounge, churning in stomach, segmentation in S.I., and haustral churing in L.I.

                     B. Chemical digestion

                      1. Breakdwon by enzymes bile, hydrochloric acid

5. Absorption- movement in bloodstream or lymph

6. Defacation- dead blood cells

The lips and cheeks and it is composed of a core of skeletal muscle covered by skin lined with nonkerintinized stratified squamous epithelium- it limits absorption, also aids in chewing, keeping food withing oral cavity, speech, ect...

Hard palate- anterior portion of palate (whole)

composed of maxilla and palentine bones, tongue forces food against it during chewing- manipulates and handles food, initiates swallowing

Soft palate- posterior portion- soft mobile flap that raises to block the nasopharynx during swallowing along w uvula

composed of a core of skeletal muscle 

Uvula- finger like projection of the soft palate; function unclear

Filiform- cone shaped- smallest in size, most numerous, no taste buds, has touch receptors (sensitve to touch)

Fungiform- mushroom shaped- middle size, middle number, tastes buds located on top of papillae

Circumvallatae- largest in size fewest in number, resemble fungiform but larger w surrounding furrow, taste buds locate on sides of the papillae

Scattered withing mucosa of tongue, palate, lips, and cheeks- found directly withing oral cavity, keep mouth moist, do not produce enzymes

Secrete saliva to keep mouth moist and keep tissue healthy and maintain pH

Lie external to oral cavity and secrete saliva into ducts leading to mouth

Only secret saliva as we; or anticipation to eat

There are 3 types:

Parotid- lies slightly anterior and inferior to ear (largest on ramus of mandible)

Submandibular- on medial surface of mandible, just anterior to mandibular angle (on inside of the body of the mandible)

Sublingual- floor of mouth just inferior to tongue

12- broad crown and four rounded cusps used for grinding (includes wisdom teeth)

Vascualr and innervated

Crown

portion above gum (gingiva)

covered in enamel (hardest substance in body)

Cementum- calcified connective tissue

muscle that closes off to prevent backflow from stomach into esophagus

Lined w nonkeratinized stratified squamous epithelium

Cardiac region- encircles the cardiac orifice at junction w/ esophagus when you swallow food it enters cardiac region

Fundus- dome-shaped, tucked under diaphragm

Body- large mid-portion of stomach

Pyloric region- terminal region of stomach (funnel shaped) Pyloric sphincter- controls entry of chyme (food) into S.I., now liquid

Globlet cells- produce an acidic mucus unique to the stomach

Parietal cells- produce HCL^-

Chief cells- produce persinogen (inactive form of pepsin) primary enzyme in stomach

Enteroendocrine cells produces gastrin, released when food enters stomach and stimultes the secretion of HCL^- and pepsinogen

Finger like projections of the mucosa- itself can be seen with the naked eye, contains capillaries and lacteals

Lined w simple columnar cililated w goblet cells

Duodenum (~5%)- portion everything empties into, receives pancreatic enzymes via the main pancratic duct, bile via the bile duct and chyme from the pyloric region of the stomach

Jejunum (~40%)

Ilieum- empties into the cecum (large intestine)

Cecum (L.I.)

Ileocecal valve

sac-like portion inferior to ileocecal valve

ileocecal valve- located at junction of ileum and cecum; control movement of chyme into L.I.

terminal portion of L.I.

opens to outside of body

Internal anal sphincter- smoot muscle

External anal shpincter- skeletal muscle

Green, alkaline (basic) liquid stored in the gallbladder, primarily involved w fats and lipids

Partially a digestive product and partially and excetory product

carry bile

right- from right lobe

left- from left lobe

common hepatic- created by a merging of the right and left hepatic ducts

Produced by the majority of the pancreas

Acini- clusters of aciner cells- produce enzymes

Released from salivary glands

Salivary amylase- starts breakdown of starch (polysaccharide into disaccharide)

Lingual lipase- starts breakdown of dieatary triglycerides- dietary fats

Secretes no enzymes only mucus

no absorption bc of time

Peristalsis- Wave-like, smooth muscle contractions that move food stuffs through entire GI tract 

HCL^- (not an enzyme) helps in protein digestion

creates a pH 2-3* inactivates salivary amylase and lingual lipase

Initatiates protien catabolism by unfolding protein structure and activating pepsin

Pesin- starches, sugars,fats

produced when HCL^- activates pepsinogen

begins breadown of peptide bonds

Very little absorption

Releases chyme into SI in small amounts over a period of time (~4 hrs)

Peristalsis (movement)

Segmentation (mixing) - oscilating, ring- like, smooth muscle contractions

Mixes chyme w digestive juices

Brings digestive products into contact w mucosa helping absorption

Stores and concentrates bile by absorbing water and ions

Releases bile into S.I. in response to the release of cholecystokinin (cck)

Released from intestinal lining in response tofaty chyme entering the deudenum

Peristalsis at a slow rate

Haustral churning (more mixing)- squishing back and forth- contraction of an individual haustrum

Mass peristalsis- strong wave beginning in transverse colon and pushing contents into rectum

No enzymes secreted, just mucus

bacteria living in the L.I. finish digestion

Ferment CHO- provide themselves w energy

Some B vitamins and Vitamin K are end products of bacterial action

Water- always through osmosis

Electrolysis( Na⁺ and Ca⁺)- simple diffusion

Vitamins

Chyme remain in L.I. for 3-10 hrs

Defacation

Lumbar reflex- intiated when feces enters the rectum

Impulses travel bk to internal anal sphincter as well to the cerebral cortex

Cerebral cortex fires causing external anal sphincter to relax