Digestive System Overview

Digestive System Overview

• The digestive system is a collection of organs that break down food for use by the body.
• It is divided into two parts: the alimentary or gastrointestinal tract and the accessory organs.

Alimentary Canal

• The alimentary canal (gastrointestinal tract) is a hollow muscular tube open at both ends.

Mouth (Oral Cavity)

• The mouth is a mucus membrane-lined cavity.
• Lips protect the anterior opening.
• Cheeks form the lateral walls.
• The palate forms the roof.
• The tongue is attached to the floor of the mouth.
• The mouth cavity has a roof (hard and soft palate) and a floor (tongue).
• It contains tongue, teeth, sublingual glands, and openings to salivary ducts.

Pharynx

• The oral cavity ends in the oropharynx.
• The oropharynx continues as the laryngopharynx which leads to the esophagus.

Esophagus

• The esophagus is a 25 cm long muscular tube.
• It begins at the end of the pharynx and ends in the stomach.
• It has cervical, thoracic, and short abdominal parts.
• It carries food from the pharynx to the stomach by peristalsis.

Stomach

• The stomach begins at the cardiac opening and ends at the pyloric opening (junction with the duodenum).
• It is divided into cardia, fundus, body, antrum, and pyloric canal.

Small Intestine

• The small intestine is the longest part of the alimentary canal (6 meters).
• Divided into duodenum, jejunum, and ileum.
• It starts at the pylorus and ends at the ileocecal junction.
• The duodenum is 25 cm long and receives the opening of the bile duct and pancreatic ducts.
• Most food absorption happens in the small intestine.
• The surface area is increased by microvilli and villi.
• Plicae circulares are large circular folds of mucosa and submucosa.
• Peyer's patches are lymphoid nodules in the distal parts of the small intestine.

Duodenum

• The duodenum has openings for the bile and pancreatic ducts.
• It digests food particles by bile from the liver and pancreatic enzymes.

Large Intestine

• The large intestine is larger in diameter than the small intestine but much shorter.
• Extends from the ileocecal junction to the anal canal.
• Parts include cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal.
• The primary functions are water and electrolyte absorption and storing the digested food residue as feces.
• The appendix is commonly inflamed and infected (appendicitis), needing appendectomy in some cases.

Accessory Organs

• Accessory organs aid in food breakdown but aren't part of the alimentary tract.
  • Teeth
  • Tongue
  • Salivary glands
  • Liver
  • Gall bladder
  • Pancreas

Salivary Glands

• Salivary glands include three pairs: parotid, sublingual, and submandibular.
• Their ducts open into the oral cavity.

Teeth

• Deciduous (baby) teeth number 20.
• Permanent teeth number 32.

Tongue

• The tongue is a mass of skeletal muscles with a mucous membrane, located in the oral cavity and oropharynx.

Pancreas

• The pancreas is a soft, pink triangular gland on the posterior abdominal wall.
• It produces digestive enzymes secreted into the duodenum.
• It's also an endocrine gland secreting insulin and glucagon.
• It is a large gland surrounded by the duodenum.
• Divided into head, neck, body, and tail.

Liver

• The liver is the largest gland in the body, located under the diaphragm, mostly on the right side.
• It has many metabolic functions.
• The digestive function of the liver is secretion of bile, which is carried through the biliary ducts to the duodenum.
• The liver has right, left, caudate, and quadrate lobes.

Gall Bladder

• The gall bladder is a small, thin-walled, green sac.
• The right and left hepatic ducts unite to form the common hepatic duct, which joins the cystic duct to form the common bile duct.
• The common bile duct opens into the duodenum.
• Divided into fundus, body, and neck.
• Its duct is called the cystic duct.

Peritoneum

• The peritoneum is the largest serous membrane in the body.
• Parietal peritoneum lines the abdominal wall; visceral peritoneum covers the organs.
• Peritoneal cavity is the space between visceral and parietal peritoneum, filled with peritoneal fluid.
• Ascites is the accumulation of excessive fluid in the peritoneal cavity.
• Major peritoneal folds include the greater omentum, falciform ligament, lesser omentum, mesentery, and mesocolon.

This quiz covers the essential components of the digestive system, including the anatomy and functions of the alimentary canal and accessory organs. It explains the parts from the mouth to the esophagus, highlighting key structures and their roles in digestion.