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| Wednesday, January 10, 2007 |
| "Digestive System" |
By :
Ns. I Made Wira, BSn.,Rn.
The organs of the digestive system
Picture :
Function of alimentary system
1. The function of the digestive system is to break down food (complex carbohydrates, proteins & fats) via hydrolysis into simpler molecules that can be used by the body’s cells.
2. Hydrolytic – uses water & enzymes.
e.g.
a. carbohydrate + water + amylase= glucose
b. proteins + water + proteases = amino acid
c. Fats + water + lipases = fatty acid & glycerol
Organs of the Digestive System
1. Alimentary Canal
• Oral cavity
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
2. Accessory Organs
* Teeth
* Tongue
* Salivary glands
* Liver
* Gallbladder
* Pancreas
Structure of the alimentary tract (from inside out)
* Tunica mucosa – squamous epithelium & columnar epithelial cells. Protection, secretion of enzymes, mucus & absorption.
* Tunica submucosa–loose connective tissue
* Tunica muscularis – mouth, pharynx & 1st part oesophagus (voluntary), peristalsis & involuntary contraction. Skeletal muscle.
* Tunica serosa – serous membrane make up connective & epithelial tissue.
Basic structure of the alimentary canal from oesophagus to anus.
5 basic activities in digestive system
* Ingestion.
* Peristalsis / propulsion – movement of food in GIT tract.
* Digestion – mechanical & chemical.
* Absorption – digestive tract to circulation.
* Defecation / elimination – indigestible.
Picture :
Mouth
* Mouth (Oral or Bucal) divisions
– Formed by the cheeks, lips (labia), hard and soft palates, and tongue.
– Receives food and saliva
– Uvula prevent food going into nasal cavity.
– Initiates digestion
Mouth
Picture :
* Teeth
– Secured in sockets (alveoli) of maxillary and mandibular bones
– Cutting and shearing food
– Incisors (4), canine (2), premolars (4) and molars (6)
* Tongue
– Accessory organ of digestion
– Manipulates food and assists in deglutition
– Senses the tastes of food
A section of a tooth
The tongue & location of papillae
Picture :
Mouth
Picture :
– Salivary Glands
– Accessory organs of digestion
• Three paired glands
1. Parotid
• Stensen’s duct
2. Submandibular
• Wharton’s duct
3. Sublingual
• Rivinus’ duct
Mouth
• Functions of Salivary Glands
- Secretion of saliva : (1,000 – 1,500 ml/day)
- Cleansing teeth
- Facilitate swallowing
- Initialing digestion
- Formation of bolus
- Dissolve food chemicals
Pharynx
Picture :
* Location
* Structure
– Throat
– Made of muscles and lined with mucous membrane
– Nasopharynx—Air only
– Oropharynx—passage of food
– Laryngopharynx—food passage and air
* Serves as a common passageway for food, liquids, and air
* Pharyngeal constrictors push the bolus toward the esophagus.
* Initiate swallowing process
Esophagus
* Location
– From pharynx (C6) to stomach (T7)
– Posterior within mediastinum posterior to trachea
– Anterior to vertebral column
* Structure
– Fibromucular tubular portion of digestive tract
– 25 cm (1 ft) long
– 2 cm (0.75 in.) diameter
– From laryngopharynx pierces through the diaghragm to oesophageal hiatus opening at the superior portion of stomach.
Esophagus
* Microscopic Structure
– Mucosa: Inner lining
– Submucosa: Esophageal glands
– mucous secretion to lubricate bolus
– Muscularis
• Superior 1/3 skeletal muscle
• Middle 1/3 skeletal and smooth muscle
• Inferior 1/3 smooth muscle
Esophagus
– There is no serosa
• Outer connective tissue
• Called Adventitia
• No digestive enzymes
• No absorption take place
• Oesophagus sphincter connects it to stomach & control passage og food.
Function
– Transports food and liquids to the stomach.
– Secret mucus.
Longitudinal section of the stomach
Stomach
Picture :
* Pouchlike digestive organ
* Between esophagus and duodenum
* In the upper left quadrant of abdominal cavity
* Immediately below diaphragm
Stomach
* Gross Structure
– J-shaped (T7-L3)
– Cardiac End
• Named by its proximity to the heart
– Pyloric End
• Funnel shaped
• Curve of the J
• Connected to the duodenum (pyloric sphincter)
– Greater Curvature
• Forms lateral surface
• 40 cm (16 in.)
– Lesser Curvature
• Forms medial surface
• 10 cm (4 in.)
Stomach – Gross Structure
* Fundus
– Above the entrance of the esophagus (gastroesophageal junction)
* Body
– Largest region
– Area between the fundus and the curve of the J
– Functions as a mixing tank for ingested food and gastric secretions
– When empty—mucosa and submucosa form longitudinal folds called rugae.
Stomach – Gross Structure
* Pyloric Antrum
– Connected to the body of the stomach
– Stomach starts to narrow
* Pyloric Sphincter
– Regulates the release of chyme (partially digested food and gastric secretions) into the duodenum.
– Prevents food from regurgitation from intestine to stomach
– 3 muscle layers – inner/oblique middle/circular, outer/longitudinal.
Small Intestine
Picture :
* Location
– Occupies all abdominal regions except the left hypochondriac and epigastric regions
– Plays primary role in digestion and absorption of nutrients
– Averages 6 m (20 ft) in length
– Diameter
• 4 cm (1.6 in) at the stomach
• 2.5 cm (1 in.) at the junction with large intestine
Small Intestine – Gross Structure
Picture :
* Duodenum (twelve fingers’ width)
– C-shaped
– Shortest and widest segment
– 25 cm (10 in.)
– Anterior to right kidney and upper three lumbar vertebrae
– “Mixing bowl”
• Receives chyme from stomach and digestive secretions from pancreas and liver.
Small Intestine – Gross Structure
* Jejunum
– About 2.5 m (8 ft) in length
– Suspended from posterior wall of peritoneum—mesentery
– Chemical and mechanical breakdown of chyme
– Absorption of nutrient
– Transportation of undigested material to large intestine
Small Intestine – Gross Structure
* Ileum
– Third and last segment of small intestine
– Longest—averaging 3.5 m (12 ft) in length
– No distinct separation from jejunum
– Ends at ileocecal valve
Small Intestine – Microscopic Structure
* Intestinal Villi
– Fingerlike projections of mucosa
– Increases total area for absortion
* Brunner’s Glands
– Limited to duodenum
– Secrete mucous
• Mucous contains buffers that help elevate the pH of the chyme
* Peyer’s Patches
– Form circular or oval patches
– Largest and most numerous in the ileum
– Fight against infections in ileum
The jejunum & ileum & their related structures
Picture :
Large Intestine
* Horseshoe-shaped
* Begins at the end of the ileum and ends at the anus
* inferior to the stomach and liver
* Almost completely frames small intestine
* 1.5 m (5 ft) length
* 7.5 cm (3 in) width
* Divided into three parts
– Cecum
– Colon
– Rectum
Large Intestine – Gross Structure
* Cecum
– First portion of large intestine, appears as a pouch
– Collects and stores material arriving from ileum
– Begins Compation
* Vermiform Appendix
– Approx 9 cm (3.5 in)
– Size and shape are quite variable
– Functions as part of the lymphatic system
Large Intestine – Ascending Colon
* Begins at superior border of the cecum
* Ascending along the right lateral and posterior wall of peritoneal cavity
* Inferior surface of liver
* Turns to the left at the Right Colic Flexure (Hepatic Flexure)
Large Intestine – Transverse Colon
* Begins at the Right Colic Flexure
* Curves anteriorly
* Crosses abdomen from right to left
* Inferior to greater curvature of stomach
* Near the spleen makes a right-angle bend, termed the Left Colic Flexure (Splenic Flexure)
Large Intestine – Descending Colon
* Proceeding inferiorly along left side of abdomen
* Firmly attached to the abdominal wall
* At the ilia fossa, enters an S-shaped segment, sigmoid colon, at the sigmoid flexure
Large Intestine – Sigmoid Colon
* Begins at the sigmoid flexure
* An S-Shaped segment of the large intestine
* 15 cm (6 in) long
* Empties into rectum
* Rectum
– Last15 cm (6 in) of digestive tract
– Expandable organ for temporary storage of fecal material
* Anal Canal
– Last portion of rectum
– Contains small longitudinal folds—anal columns
– Ends at anus
Large Intestine
* Function
– Reabsorption of water and electrolytes
– Compaction of intestinal contents into feces
– Absorption of important vitamins produced by bacterial action
– Storing of fecal material before defecation
* Large intestine receives blood from tributaries of the superior and inferior mesenteric arteries
* Venous blood is collected by superior and inferior mesenteric veins.
Liver
Picture ;
* Location
– Right hypochondriac and epigastric regions
* Structure
– Very soft and flaccid
– Largest gland of body
– Weights 1.5 kg (3.3 lb)
* Function
– More than 200 different functions
– Production of bile
• 1 liter per day
– Detoxification
• Extract absorbed nutrients or toxins from blood
The liver- anterior & posterior view
Picture :
Gall Bladder
* Location
– In a recess (fossa)
– In the visceral surface of the right lobe of the liver.
* Structure
– Hollow, pear-shaped, muscular organ
– Three regions: fundus, body and neck
* Function
• Bile storage
– Bile modification
Biliary Tract
* Location
– Caudoposteriorly
* Structure
– Joins hepatic duct
– Form common bile duct (7.5 cm)
* Function
– Drains bile into duodeum (ampulla)
• Hepatic ducts
• Cystic ducts
• Common bile duct
• Hepato-pancreatic duct
Functions of the liver
1. Manufacture anticoagulant – heparin, plasma protein, prothrombin & thrombin.
2. Kupffer’s cells–phargocytose bacteria,old & worn out white blood cells & RBC.
3. Enzymes – break down poisons, convert ammonia to urea & excreted by kidneys.
4. Convert excess glucose to glycogen.
5. Stored glycogen, copper, iron & vit. A,D,E,K.
6. Bile to break down fat.
Pancreas
* Location
– Posterior to stomach
– Laterally from duodenum toward spleen
* Gross Structure
– Broad head lies within loop of the duodenum
– Surface has a lumpy and nodular texture
* Orientation
– Slender body extends transversely toward spleen
Pancreas
* Microscopic Structure
– Heterocrine Gland
• Endocrine
– Insulin
– Glucagon
• Exocrine
– Alkaline digestive juices (digestive enzymes)
* Function
– Produce enzymes and hormones
– Islets of Langerhans produce insulin |
posted by I Made Wiradiana @ 10:24 AM  | Permalink
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