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Observe a cross section through the mammalian intestine and identify four layers; the mucosa folded to form villi, the submucosa (the region containing larger blood vessels and lymphatics of the gut), the muscularis (the layers of smooth muscles - an inner circular layer and an outer longitudinal layer), and the serosa (the outer thin connective tissue layer of the intestine).
This is the muscle type found in the visceral organs e.g. intestine and other organs and is under control of the autonomic nervous system. Smooth muscle cells are much smaller than the long syncytial striated muscle cells. Note the spindle shape of each cell, the sausage-shaped nucleus and the cytoplasm. Myofilaments (the contractile components), are very small and are only visible with the electron microscope.
The liver arises as an out-pouching of the wall of the embryonic gut lying in the pathway of the vitelline veins. The parenchyma of the liver is divided into lobules by septa of connective tissues which are continuous with the superficial covering of the whole liver. The hepatocytes are polyhedral in shape and possess finely granular cytoplasm. Cell membranes are indistinct. The round, vesicular nuclei have prominent nucleoli and often two nuclei may be seen in one cell. Fat droplets and glycogen granules may be demonstrated in the hepatic cells by special techniques.
