Essentials of Anatomy and Physiology

375

Small intestine

Mucosa

Submucosa

External

muscle

layer

Serosa

Epithelium

Lacteal

Capillary

network

Lymph

nodule

Lymphatic

vessel

Smooth

muscle

Venule

Arteriole

Meissner's

plexus

Circular

smooth muscle

Longitudinal

smooth muscle

Auerbach's

plexus

Parietal

peritoneum

Transverse

colon

Greater

omentum

Uterus

Bladder

Diaphragm

Liver

Pancreas

Stomach

Duodenum

Mesentery

Small intestine

Sigmoid colon

Rectum

A

B

Figure 16–4. (A) The four layers of the wall of the
alimentary tube. A small part of the wall of the small
intestine has been magnified to show the four layers
typical of the alimentary tube. (B) Sagittal section
through the abdomen showing the relationship of the
peritoneum and mesentery to the abdominal organs.
QUESTION:What is the function of the external mus-
cle layer?