The intestine | CHAPTER 3 | Anatomy and Physiology

The intestine- The course is designed for the basic understanding of anatomical structures and physiological functions of human body, musculoskeletal system, digestive system, respiratory system; cardiovascular system; urinary system, endocrine system, reproductive system, nervous system, hematologic system, sensory organs, integumentary system, and immune system.The aim of the course is to acquire knowledge and skills regarding anatomy and physiology.

The intestine

The intestine is the longest part of the digestive system. It is mainly divided into two parts:-

1. Small intestine:-

• Duodenum (about 25 cm)
• Jejunum (about 2 m)
• lleum (about 3 cm)

2. Large intestine:-

• Caecum
• Vermiform appendix
• Ascending colon
• Transverse colon
• Descending colon
• Sigmoid colon
• Rectum and Anal canal

Functions of small intestine

1. Mechanical functions: The mixing and propulsive movement of the small intestine help in through mixing of chyme with the digestive juices (pancreatic juice, bile juice and succus entericus) and propel it towards the large intestine.
2. Digestive functions: Completion of chemical digestion of carbohydrates, protein and fats.
3. Absorptive functions:- The end products of carbohydrates, protein and fats are absorbed through portal system or through the lymph.
4. Hormonal function: The small intestine secretes certain hormones as enterogastrone, secretine and cholecystokinin(CCK).
5. Protective function: The mucus secreted into the succus entericus protects the intestine wall from the gastric acid chyme.
6. Hydrolytic function: The succus entericus provides necessary water which help various food particles. to digest

(Ref:- K. Indu, Text book of Anatomy and Physiology for Nurses, 1 edition,P-290)

Functions of large intestine

1. Secretory function: The large intestine secretion mainly comprise mucin which helps to lubricate the faecal matter.
2. Synthesis functions: The bacterial flora of the large intestine sysnthesize folic acid, vitamin B and vitamin-K.
3. Absorptive functions: The large intestine absorbs water, folic acid, vitamin B2, vitamin-K, electrolytes and organic substances like glucose, alcohol and some drugs like anaesthetic agents, sedatives and steroids can also be absorbed in large intestine.
4. Excretory function:-

• Heavy metals like mercury, lead, bismuth and arsenic are secreted by large intestine through the faecs.
• Mass movement. A strong peristaltic wave that beginsan the middle of the colon and drives the colonic contents into the rectum
• Defaecation is followed by mass movement that forces the contents of the sigmoid colon into the rectum. It is also under nervous (reflex) contron.

(Ref.- K. Indu, Text book of Anatomy and Physiology for Nurses, 1″ edition P-297)

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