MOVEMENTS OF SMALL INTESTINE

Four Types of movements:1. Mixing Movements (To mix CHYME with juices): a. Segmentation movements b.Pendular movements2. Propulsive Movements (to propel food forward in

GIT) a. Peristalsis b. Peristalsis rush3. Peristalsis in fasting- Migrating Motor Complex4. Movements of Villi

MIXING MOVEMENTS OF SMALL INTESTINE

1. SEGMENTATION COINTRACTIONS: a. They occur rhythmically at regular spaced intervals along a part of intestine of length 1-5 cm. The segments of intestine in between the contracted segments remain relaxed & are of equal length to contracted segment. So alternate segments of Contraction & relaxation occurs giving appearance of a chain of sausages. See Diagram nxt slide2. After sometime the contracted parts relax & relaxed parts contract.3. Therefore segmentation movements chops the chyme many times. Helping tomix chyme with digestive juices.

SEGMENTAL CONTRATIONS OF SMALL INETESTINE

2. Pendular Movement:Small portion of intestine sweep forward and backward or upward & downward resembling pendulum of a clock and help in mixing chyme with digestive juices.

B. Propulsive Movements:They are involved in pushing the chyme in the aboral direction of intestine 1. Peristalsis:a. It is defines as the wave of contraction followed by wave of

Relaxation, which travel in aboral direction. It is caused by stimulation of smooth muscles of small intestine.

b. It travels from point of stimulation to both sides but under normal Conditions progress towards oral direction is abolished And Contractions Travel only in Anal direction. c. Starling Law of Intestine: the response of the intestine for a local stimulus consists of a contraction of smooth muscle above and relaxation below the stimulus area.(see diagram nxt TO nxt slide)

d. The peristaltic contractions start at any point and travel toward the anus at a velocity of 0.5 to 2.0 cm/sec, faster in the proximal intestine and slower in the terminal intestine. They normally are very weak and usually die out after traveling only 3 to 5 cms, so that forward movement of the chyme is very slow, so slow in fact that net movement along the small intestine normally averages only 1 cm/min. This means that 3 to 5 hours are required for passage of chyme from the pylorus to the ileocecal valve

Peristaltic Rush:

Although peristalsis in the small intestine is normally weak, intense irritation of the intestinal mucosa, as occurs in some severe cases of infectious diarrhea, can cause both powerful and rapid peristalsis, called the peristaltic rush.

3.Movements of Villi:Smooth muscle fibres extend from intestine into villi so the villi also simultaneously show movements when peristalsis occurs.Movements of villi- Shortening & elongation- & are under effect of hormone Villikinin form small intestine.Which help ina. emptying Lymph from central lacteal of villi into lymphaticsb. In increasing surface area of villi needed for more effetive absorption