Digestive system

Function the Digestive System

· Digestion

· Breakdown of ingested food

· Absorption

· Passage of nutrients into the blood

· Metabolism

· Production of cellular energy (ATP)

The Digestive System

· Two main groups

· Alimentary canal.

· Accessory digestive organs.

Organs of the Alimentary Canal

· Mouth

· Pharynx

· Esophagus

· Stomach

· Small intestine

· Large intestine

· Anus

Mouth (Oral Cavity)

· Vestibule; space between lips externally and teeth and gums internally.

· Oral cavity proper; area surrounded by the teeth and gums, containing the tongue.

Mouth (Oral Cavity)

· Lips (labia); protect the anterior opening

· Cheeks; form the lateral walls.

· Hard palate; forms the anterior roof.

· Soft palate; forms the posterior roof.

· Uvula; fleshy projection of the soft palate.

· Tongue; lies in the middle of the cavity attached at hyoid and styloid processes of the skull, and by the lingual frenulum

tongue

Pharynx

· Muscular tube extends from base of skull to be continues with the esophagus.

· It is divided into;

· Nasopharynx , posterior to nasal cavity

· Oropharynx , posterior to oral cavity

· Laryngopharynx , posterior to larynx

Esophagus

· Muscular tube, continuation of the pharynx.

· Runs from pharynx. through the thoracic cavity, piercing the diaphragm, to end in the stomach.

· Conducts food and fluid.

Stomach

· Located on the left side of the upper part of the abdominal cavity.

· Composed of upper and lower ends, anterior and posterior surfaces, lesser and greater curves.

· Divided into the following regions;

· Cardiac region; near the upper end, (heart).

· Fundus

· Body

· Phylorus; funnel-shaped terminal end.

peritoneum

· Serous membranes lines the abdominal and pelvic cavities and covers the related organs.

· It is attached to the stomach curves.

· Lesser omentum; attaches the liver to the lesser curvature.

· Greater omentum; attaches the greater curvature to the transverse colon, and then to the posterior body wall.

· Contains fat, blood vessels, lymphatic vessels, lymph nodes and nerve plexuses;

· Help to insulate, cushion, and protect abdominal organs.

· Transmit blood, lymph and nerve supply to the abdominal organs.

Small Intestine

· Muscular tube extending form the stomach (the pyloric sphincter) to the commencement of the large intestine (ileocecal valve).

· The body’s major digestive organ.

· Site of nutrient absorption into the blood stream.

Subdivisions of the Small Intestine

Fixed part;

· Duodenum· Attached to the pyloric

end of the stomach.

· C shape, curves around the head of the pancreas.

· It is the site for digestion.

Subdivisions of the Small Intestine

Mobile part;

· Jejunum· Constitutes 2/5 of the length.

· Attaches to the duodenum.

· Ileum· Constitutes 3/5 of the length.

· Extends from jejunum to commencement of large intestine, (ileocecal valve).

· Both Jejunum, and Ileum are the site for digestion.

Large Intestine

· Large diameter muscular tube, extends from the end of the small intestine to the rectum.

· Larger in diameter, but shorter than the small intestine.

· Frames the small intestine in the abdominal cavity.

Structures of the Large Intestine

· Cecum – saclike first part of the large intestine.

· Appendix. hangs from the cecum.

Structures of the Large Intestine

· Colon

· Ascending

· Transverse

· Descending

· S-shaped sigmoidal

· Rectum

· Anus; external body opening

Accessory Digestive Organs· Salivary glands

· Teeth

· Pancreas

· Liver

· Gall bladder

Salivary glands

· Saliva-producing glands are three pairs.

· Parotid glands, located anterior to ears.

· Submandibular glands, below the mandible.

· Sublingual glands, below the tongue.

Teeth

· Humans have two sets of teeth

· Deciduous (baby or milk) teeth 20 teeth are fully formed by age two.

· Permanent , 32 teeth, fully formed by 20 years.

Classification of Teeth

Slide 14.36b

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 14.9

Pancreaso Endocrine and exocrine gland .o Lies behind the stomach.oComposed of head, body, tail and uncinate process.oIts head lies in the concavity of the duodenum.oThe body Lies behind the stomach.oIts tail lies in relation to the spleen

Liver

· Largest gland in the body

· Located on the right side of the upper part of the abdominal cavity under the diaphragm

· Consists of four lobes

· Connected to the gall bladder via the common hepatic duct

Gall Bladder

· It is a small sac found in hollow fossa of inferior surface of the liver.

· Connected to the liver via the common hepatic duct

· Stores, and concentrates bile.

· Connected to the duodenum by the bile duct.

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