DIGESTIVE SYSTEM

FUNCTIONS1. Ingestion.2. Digestion.3. Absorption.4. Defecation.

COMPONENTS(1) Alimentary

(Gastrointestinal) tract which performs the whole digestive functions.

(2) Accessory organs: assist the process of digestive break down.

ALIMENTARY CANAL (GIT)Muscular tube. Length: In the cadaver 9

m.In the living person , is

shorter because of the muscle tone.

Continuous, Coiled & Hollow.

Winds around the ventral body cavity.

Opens at both ends.

COMPONENTS OF GITMouth.Pharynx.Esophagus.Stomach.Small intestine.

Large intestine.

ACESSORY DIGESTIVE ORGANSSalivary glands.

Teeth.Liver & Gall bladder.

Pancreas.

MOUTH (oral cavity)A mucous membrane

lined cavity.It is the site of food

entry.Boundaries :Anterior : lips (labia). Lateral : cheeks.Roof : hard and soft

palates.Floor : tongue.

ORAL CAVITYDivided into :Vestibule :A space between the

lips and cheeks externally and the teeth and gums internally.

Oral cavity proper: :The area contained

by the teeth.It contains

Lymphoid tissue :Palatine tonsil and

lingual tonsil.

PHARYNXOropharynx and

Laryngopharynx are parts of the alimentary tract.

Food is propelled through the pharynx into the esophagus by peristalsis.

ESOPHAGUSA muscular tube

25 cm (10) inches long.

Begins as a continuation of the pharynx.

Terminates in the stomach.

It conducts food to the stomach.

STOMACH Position : On the left side

of the abdominal cavity under the liver and diaphragm.

Shape : C – shaped.

Length : 25 cm

PARTS1. Cardiac region : near

the heart.2. Fundus : the

expanded part lateral to the cardiac region.

3. Body : mid portion. 4. Pylorus: the

terminal part of the stomach. divided into :

Antrum.Pyloric canal : cavity

of pylorus.

CURVATURESGreater : convex

lateral surface of the stomach.

Lesser : concave medial surface.

SPHINCTERSPhysiological:Cardioesophageal:Where the

esophagus opens into the stomach.

Anatomical:Pyloric :where the stomach

is continuous with the small intestine.

PERITONEUMLesser omentum :It extends between

the liver and the lesser curvature.

Greater omentum :It extends between

the greater curvature and the transverse colon .

SMALL INTESTINEIt is the major

digestive organ (2.5 -7) m in the living person.

Extends: from the Pyloric

sphincter to the Ileocecal valve.

Divided into:Duodenum,

Jujenum & Ileum.

DUODENUMThe shortest part of

the small intestine (nearly 5%).

C-shaped.Receives the

openings of the pancreatic and bile ducts.

JUJENUM & ILEUM2. JUJENUM :Contributes nearly

40% of the small intestine.

3. ILEUM :Contributes nearly

60% of the small intestine.

It joins the large intestine at the ileocecal valve.

LARGE INTESTINELarger in diameter and

Shorter in length (1.5) m than the small intestine.

It frames the small intestine on three sides.

It extends from the Ileocecal valve to the Anus.

It dries the indigestible food residue and eliminates it out as feces.

CRITERIA(1) Teniae Coli : three

bands of muscle that can be seen externally. It is formed from the longitudinal muscle layer.

(2) Haustra : small pocket like sacs in the wall due to the muscle tone.

(3) Appendices epiploicae:

peritoneal folds full of with fat.

PARTS(a) Cecum : first part of the

large intestine.(b) Appendix : A wormlike, It hangs

from the cecum. It is an ideal site for

bacteria to multiply and accumulate .

COLON1. Ascending: It travels up the right

side of the abdominal cavity.

It makes a turn, the right colic (hepatic) flexure.

2.TransverseIt travels across the

abdominal cavity.It makes the left colic

(splenic ) flexure.

COLONDescendingIt travels down the left

side of the abdominal cavity and enters the pelvis.

Sigmoid (pelvic) It is S- shaped and lies

in the pelvis. Rectum.

Anal Canal and Anus.

ANAL SPHINCTERSThe anal canal has

two sphincters :1. External

(voluntary) formed of skeletal muscle.

2. Internal (involuntary) formed of smooth muscle.

TEETHDeciduous (milk) teeth :They begin to appear

about (6) months.The first teeth to erupt are

the lower central incisors.At the age of two years

they are (20) in number.The milky teeth fall out

between ages (6-12) years.Permanent teeth :Fully erupted at the end of

adolescence. They are 32 in number.

Third molars (wisdom) Erupt later at ages (17 –25) years.

SALIVARY GLANDSThree pairs of salivary

glands(1) Parotid glands They are the largest.They lie anterior to the

ear.They empty their secretion

into the vestibule.(2) Submandibular glands.(3) Sublingual glands.They empty their

secretions into the floor of the mouth cavity proper.

LIVERThe largest gland

in the body (exocrine & endocrine).

It lies in the right side of the body under cover of the diaphragm.

It is formed of (4) lobes.

LIVERIt is suspended

to the diaphragm and anterior abdominal wall by the peritoneal fold (Falciform Ligament).

FUNCTIONSExocrine gland: It produces bile.Bile leaves the liver

through the common hepatic duct.

Enters the duodenum through the bile duct.

Bile salts are important for the metabolism of fat.

Endocrine gland:Produces vitamin A,

stores glycogen.

GALL BLADDERA small thin walled

green sac.Lies on the inferior

surface of the liver.Stores and

concentrates bile.Bile enters and leave

the gall bladder through the cystic duct.

PANCREASIt is a soft pink

triangular gland.It is retroperitoneal.It extends from the

spleen to the duodenum across the posterior abdominal wall.

Functions :1. Endocrine :

production of insulin and glucagon hormones.

2. Exocrine :It produces enzymes

that enter the duodenum through the pancreatic ducts.

PANCREATIC DUCTSMain pancreatic

duct: Joins the bile duct to form the Hepato pancreatic ampulla.

Both ducts open together through the duodenal papilla in the duodenum.

Accessory pancreatic duct:

Opens separately.