Digestive System

Purpose of the digestive system

Purpose of the digestive system

to provide a continous supply of H2o,electolytes and nutrients

Feces

non-absorbed food material “undigestible material”

walls of the digestive system

walls

Longitudinal muscle layer

runs length wise in the organ

Circular muscle

runs around the organ

Sub Mucosa layer

layer of connective tissue under the mucosa

Mucosa layer

layer of mucous membrane that secretes

Divisions of the stomach

divisions

Fundus

enlarged portion above asophagus

Body

central portion of the stomach

Pylorus

lower part of stomach

Organs of the gastrointestinal tract

organs

mouth

oral cavity

Pharynx

tube through which a bolus go through

esophagus

tube that extends pharynx to the stomach

stomach

stors food for 2-3 hours

small intestine

mixes food further

large intestine

approximetly 6cm in diameter 1.5 meters long

Accessory organs

organs not needed to live

Salivary Glands

secrete saliva

Vermiform appendix

vestigal organ below cecum

liver

largest gland in the body stores blood

hepatocytes

liver cells

gallbladder

produces digestive enzymes runs behind stomach to spleen

pancreas

lies on undersurface of liver ejects bile

Structures of the oral cavity

-lips- manipulative folds that close the opening of the mouth

Cheeks

lateral boundries of the oral cavity; covered with mucous membrane

palettes

hard at the anterior and has bone behind it

-soft at the rear separates the mouth from the nasopharynx

-uvula- hangs down at the back of the soft palate

-a, the tongue-solid mass of skeletal muscle that keeps food between teeth- organs of mastication.

-composed of the crown- exposed portion covered by enamel

-neck-narrow portion that joints crown to root

-roots- fits into the socket of the alveolar process of the bone

-internally composed of dentin surrounding pulp cavity

Types of teeth

teeth

incisors

flattened teeth at anterior which cut material

canines

sharp,pointed teeth for ripping

premolars

reletively flattened teeth used for grinding

Molars

very large flat teeth for grinding

mastication

chewing

reduces size of food particles and increases surface area -mechanical digestion

mixes food with saliva for ease of swallowing.

Salivary glands

-produce digestive enzymes and mucus=saliva

Parotoid glands

largest, located outside bone in front of ear.

produce watery saliva containing enzymes and enzymes.

Subligual glands

located below; produce mucous type of saliva

Pharynx

tube through which a bolus of food passes when moved from the esophagus during deglutination

-deglutination=swallowing

oral stage

voluntarily controlled

formation of food bolus by tongue

-tongue pushes food against palate.

pharyngeal stage

oropharynx to esophagus

oral cavity closed by tongue, combination of contractions and gravity move bolus into esophagus

esophagus-esophagus to stomach

peristalsis

-inoluntary rythmic contractions that propell food in gi tract stimulated by distension

Segmentation

mixing movement that causes that causes back and forth movement within a single area of the gi tract; mixes food with enzymes and brings digested food into contact with mucosa to facilitate absorbtion

esophagus

-tube that extends from pharynx to the stomach

-reverse peristalsis happens when food enters botoom of esophagus

-cadiac sphincter controls movement of food into stomach

-heartburn occcurs when acid comes through

-gastroephageal reflux disease.GERD

Stomach

-stores large amounts of food for 2-3 hours

-mixes food with gastric secreations including gastric juice and hydrochloric acid PH 1-3

-oblique muscle layer helps in mixing movements

-food mixes with gastric juices=chyme

-absorbs alchol,some drugs,aspirin can breach the mucosal barrier and cause bleeding

-cekks are constantly shedding-newlining every 3 day

-pyloric sphincter controls exit to small intestine

stomach wall

gastric mucosa

rugae marked by gastric pits

gastric glands-secretes gastric juice

chief cells-located in gastric glands;secrete the enzyme of gastric juice

parietal cells-in gastric glands;secrete HCL

-endocrine cells secrete gastrin

Small intestine

periostalic waves move chyme; segmentation movements mix food further

-approxiematley 2.5 cm in diameter and 7m (22ft’9 inches in length

three divisions.

Duodenum

upper portions-adds secreations,digest

Jejunum

secretory and digestive functions

ileum

digestive and absorptive function

villi with microvilli increse -each contains an arteriole,venule,and lacteal for absorbing nutrients.

Large intestine -colon

approxiemately 6cm. diameter;1.5 m (5ft) long

cecum

blind sac located below leoceal where the ileum empties into colon

veriform appendix

vestigal organ below cecum

ascending colon

vertical section on rigtht side of abdomena

tranverse colon

crosses horizontally across the abdomen above the small intestine

descending colon

vertical section on left side of abdomen

sigmoid

connects descending colon to rectum

rectum

last 7-8 inches of intestinal tube- stores fecal material for defication

peritoneum

-sheet of serous membrane that helps to hold intestines in place

mesentary

membrane between folds of small intestines,allows free movementrr

tranverse mesocolon

extension of peritoneum that holds tranverse colon place

Accessory organs

liver,pancreas,gallbladder

liver

largest gland in the body(1.5 kg), just below diaphragm

blood within liver is within spaces called sinusoids

Bile ducts

bile ducts within the liver carry bile to the gallbladder

detoxifies many substances such as alcohol and barbiturates

secrete bile in form of bile salts

helps in metabolism of fats,carbohydrates, and proteins

stores iron some vitamins and glucose

form many blood components:erythrocytes in embryo,plasma proteins,prothrombin and other clotting factors

sinusoids

blood within liver is within spaces called sinusoids

hepatocytes

liver cells

Pancreas

runs from duodenum,behind stomach,to spleen

exocrine gland

portion produces digestive enzymes

which travel to duodenum through the pancreatic duct. Endocrine portion

secretes insulin and glucagon directly into the capillaries

Gallbladder

lies on undersurface of liver

stores and concentrates bile

ejects concentrated bile through bile duct to duodenum

Mechanical digestion

changes the physical state of food large solif pieces to small pieces

so that chemical digestion is more efficient

mastication and deglutination

peristalsis and segmentation

Chemical digestion

chemical breakdown of food by enzymes

enzymes are protein catalysts

are specific in what they digest

enzymes are protein catalyst

are specific in what they digest

enzymes work best at specific PH

Carbohydrate digestion

used primary by the body as energy sources

must be broken down into mono saccharides simple sugars to be used by cells

-glucose , fructose and galactose

polysaccharides to disaccharides to monosaccharides.

salivary amylase-in saliva begins carbohydrate digestion

pancreatic amylase added in the small intestine begins the digestion of carbohydrates that aren’t affected by saliva amylase

ex-sucrase,maltase, and lactose complete the digestion into monosaccharides

-these enzymes are located within the epithelial cells covering the villi and preform contact digestion

protein digestion

proteins must be digested into amino acids to be absorbed and utilized

proteases work on proteins and break them into intermidiate product such as peptides

digestion begins in the stomach with pepsin wich breaks large polypeptides into smaller polypeptides and single amino acids

trypsin and chymotrpsin produced by the pancrease continue protein digestion in the small intestine

-peptidase anzymes by seperating individual amino acids

complete protein digestion

Lipid digestion

since fats marew insoluble in wate they must be emulsified before they can be digested

lecithin and bile emulsify oilsa and fats in smallintestine-form tiny speres call micelles

all fat digestion takes place in thge small intestion

lipases formed by pancreas digest fats

final products of fat digestion=fatty acids,monoglycerides,nd glycerol

Metabolisim

sum of all chemical reaction in body

catabolisim

decomposition process

breaks food into small molecules

realses energy which is useful if first transferred to high energy bond og ATP

ATP highh energy bonds are easily broken and supply energy for cell reaction

Anabolisim

cibstructive reactions

synthesizaes larege molecules celluar products from smaller molecules

require energy which it gets from atp

Glycolsis

splits one glucose into pyruvic acids

occurs in cytoplasm

anerobic no o2

prepares sugar for krebs cycle

1g=2pa +atp +heat

Krebs cycle

convery 2 Pa in 6 co2

occurs in mitochondria

aeribuc

cycle stops without oxygen

glycogenesis

forms glycogen by ccombining sugar

occurs when glycosis mechanics are occupied

Glycogenolysis

split glycogen to form glucose

in response to low blood sugar

Gluconeogenesis

new sugar formed from proteins and fate

Eletion transport o

occurs in mito

o2 required

uses products of krebs cycle to produce lots of ATp

amino acids used to produce sugar

six atp are used in production

xdvd

prancreatic islets

secrete

insulin

decreses blood sugar by helping cells absorb it

glucagon

increases blood sugar ny increasing rate of glycogenolysis

during starvation cotisole promotes glyconeogenesis protein breakdown in muscle,supplies amino acids to the liver

ACTH

stimulates protein mobilization and gluconeogenesis.

Catabolsism

fatty acids broken in krebs cycle

2x as much rnrtgy as carbs

Anabolisim

syntheseis of lipids(triglycerides and cholesterol)

triglycerides are stored as fat

only sats fatty acids and be synthesized

essential fatty acids must enter with diet

Protein metabolisim

is primary- proteins are tissue building foods

proteins are synthesides by ribosomes

-every cell makes its own structural proteins and enzymes

-some build special proteins for export

-proteins are used for growth reproduction,tissue regainand replacement

Metabolic rate

amount of energy used by the body within a given time

rate of which an organisim uses food by cellulare respiation

exspressed as kcal/hour

Basal metabolic rate

amount of energy used with no action

affected by size,sex,age,thyroid,body temp

kcal per lb of fat

3,500 kcal in a pound

regulating food intake

hypothalmus-controls hungrt

appetite center neurons who bring hunger

satiety center-neurons whos pulses decrease appetite

increase blood tempincreased blood temp = not hungry

glucostatic theory -increased in blood sugar=hungry

Diarreah

increases motility of small intestine

constipation

contents of lower colon and rectum move slow

Mumps

viral disease charecterizes by swelling parotoid glands

Tooth decay

caries

decay occurs on tooth surfaces where food bres acid secreting bacteria and plaque communicatrion

gallstones

solid material and cholesterol

ulcers

wound in a membrane caused by tissue deconstruction

helicobacter pylori cause ulcers

hemmorhoids

caused by tension