Anatomy · MU Sofia

Internal Organs+Glands · 53. Alimentary system - overview and development

Walks through the organs of the digestive tract in order, from mouth and pharynx through oesophagus, stomach, spleen, liver, gallbladder and pancreas to the small and large intestines, with their functions. It also gives the arterial blood supply for the foregut, midgut and hindgut, and outlines development from the endoderm from the third week, listing the structures each part gives rise to.

Inside: 4 sections · 4 labelled pictures · 10 flashcards · 3 min

Topic 50 of 264 in the MU Sofia syllabus for Anatomy (Dental Medicine, Year 2). The free AceMed note covers it in 4 sections, about 444 words (3 min of reading), with 10 flashcards.

In this note

  1. DIGESTIVE SYSTEM
  2. Components :
  3. Blood supply
  4. Development :

Components :

→ Primary organs :

1) Mouth :

Contains structures that start digestion: teeth (choping the food), salivary glands (secrete saliva that contain enzymes that start chemical digestion of sugar and fats), tongue (detects taste, pushes bolus towards the pharynx)

2) Pharynx

Conducts the food to the esophagus

3) Esophagus :

Muscular tube that conduct the bolus to the stomach; it has upper sphincter (opens with swallow reflex and allows the bolus to enter the esophagus) and lower sphincter (controls emptying of the esophagus content to the stomach)

4) Stomach

Function - secretion of gastric acid (hydrochloric acid + sodium chloride + pepsine) that digests proteins and converts bolus to chyme

Parts - cardia (where content of the esophagus empties into stomach), fundus (upper curved part), body (main, central region), pylorus (empties the chyme into the duodenum)

5) Spleen

Breaks down spent erythrocytes → production of bilirubin → bilirubin sent to the liver → secreted in the bile

6) Liver

Main functions: detoxication of metabolytes, synthesis of proteins, production of biochemicals needed for digestion → regulation of body's metabolism and energy storage

7) Gallbladder

Stores the bile and empties it into the duodenum from where it partially eliminates via defecation

8) Pancreas

Secretes insulin when sugar levels are high, secretes glucagon when sugar levels are low, secretes pancreatic juice (tripsinogen, chymotripsinogen, elastase, amilase etc.) into the duodenum where it digests the chyme

9) Small intestine

  • Duodenum - mixes chyme with bile, secretes bicarbonates to rise pH in order to activate pancreatic enzymes which digest the chyme
  • Jejunum - absorbs small nutrients that have been previously digested in duodenum
  • Ileum - absorbs vitamin B12, bile salts and all necessary materia that were not absorbed in jejunum
  • Cecum - a pouch that marks division between small and large intestines → connects the ileum with ascending colon

10) Large intestine

  • Ascending colon - absorbs water from content and moves in to the transverse colon by peristalsis
  • Transverse colon - extends from hepatic flexure to the splenic flexure; absorbs water and salts
  • Descending colon - extends from splenic flexure to the sigmoid colon; stores feces that will be emptied into the sigmoid colon
  • Sigmoid colon - contracts to increase pressure inside the colon, causing the stool to move into the rectum

→ Accessory organs : teeth / tongue / salivary glands liver, pancreas & gallbladder.

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