Britannica Illustrated Science Library: Human Body I by Encyclopedia Britannica

Author:Encyclopedia Britannica [Britannica, Encyclopedia]
Language: eng
Format: epub
Published: 2011-10-29T23:50:37+00:00

56 INTERNAL SYSTEMS AND ORGANS

HUMAN BODY I 57

Large and Small Intestine

Differences and Similarities

The small intestine is longer than the large

and the large intestine averages 5 feet (1.5 m).

intestine. The length of the small intestine is Their respective composition and functions

between 20 and 23 feet (between 6 and 7 m),

are complementary.

The longest part of the digestive tract. It is about 26

to 30 feet (8 to 9 m) long and runs from the stomach SEROSA

The external protective

to the anus. The small intestine receives the food membrane in both

LARGE

from the stomach. Digestion continues through enzyme SUBMUCOSA

INTESTINE

In both, the loose covering

activity, which completes the chemical breakdown of the food.

with vessels and nerves

Then the definitive process of selection begins: the walls of MUCOSA

the small intestine absorb the nutrients derived from the It is thin and absorbs

nutrients via projections

chemical transformation of the food. The nutrients then or hairs.

Absorbent fat that

pass into the bloodstream. Waste substances, on the excretes mucus

other hand, will go to the large intestine. There the MUSCULAR

Thin muscle fibers that are

final stage of the digestive process will occur: the SMALL

longitudinal externally and

formation of the feces to be excreted.

circular internally. The

INTESTINE

fibers are also covered

with hairs, maximizing the

TRANSVERSE

area of the mucosa.

COLON

Fatty rigid layer that mixes

The undigested

and pushes the feces

remains begin

to be

The Union of Both

transformed

ASCENDING

into feces.

The small and large intestines join at the section called the ileum (which is the final section of the small intestine; the COLON

duodenum and jejunum come before the ileum). The iliac valve The water and

mineral salts

DESCENDING

acts as a door between the small intestine and large intestine, or Villa

are absorbed

COLON

colon. The ileum terminates in the caecum (of the large intestine).

along the

The feces are

The ileum measures approximately 13 feet (4 m) in length. Its The internal wall of the small

villus is covered by a cellular layer that

length of the

solidified and

primary function is the absorption of vitamin B12 and biliary intestine is covered with millions of

absorbs nutrients. Together with epithelial

large intestine

accumulate

salts. The primary function of the large intestine is the absorption hairlike structures called villi. Each one has cells, the villi function to increase the

in a process

before being

of water and electrolytes that arrive from the ileum.

a lymphatic vessel and a network of

surface area of the intestine and optimize

that removes

expelled.

vessels that deliver nutrients to it. Each

the absorption of nutrients.

water from the

TAENIA MUSCLE

digestive waste.

HAUSTRUM

DUODENUM

OF THE

ILEOCECAL

VILLA

LYMPHATIC

ARTERIAL

VENOUS

VALVE

The initial

COLON

CAPILLARY

CAPILLARY

CAPILLARY

relaxes

section of the

between meals,

small intestine,

allowing the

to which the

flow to

secretions of

accelerate.

the pancreas

JEJUNUM

and the liver

The intermediate

are directed

part of the small

ILEUM

intestine, which

links the

duodenum with

the ileum

CAECUM

APPENDIX

Initial

section of

the large

intestine

Opening of the

appendix

MUCOSA

WATER THAT ENTERS

WATER REABSORBED BY THE

THE ALIMENTARY CANAL

ALIMENTARY CANAL

SUBMUCOSA

SIGMOID COLON

In fluid ounces

In fluid ounces

contains a structure

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