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At the anus, there are two anal sphincters which control the exit of feces from the body, the internal anal sphincter and external anal sphincter. The inner sphincter is involuntary and the outer is voluntary. The microscopic precapillary sphincters function to control the blood flow into each capillary in response to local metabolic activity. [1]
The sea slug Pleurobranchaea meckelii respires using a gill which is visible in this view of the right side of the animal. In gastropods in many ancient lineages, the gills are bipectinate, having an overall shape that is similar to a bird's feather, with narrow filaments projecting either side of a central stalk.
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies greatly, depending on the size of the organism, the environment in which it lives and its evolutionary ...
The cells were first noted by Henle in 1837 when studying the lining of the small intestine, seen to be mucus producing by Leydig in 1857 (who was examining the epidermis of fish), and were given their name by Schulze in 1867, [24] [25] Schulze chose the descriptive name "goblet" because of the shape of the cell, rather than a functional name ...
The anal canal is the part that connects the rectum to the anus, located below the level of the pelvic diaphragm. [1] It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. As the final functional segment of the bowel, it functions to regulate release of excrement by two muscular sphincter complexes ...
The sigmoid colon is the part of the large intestine after the descending colon and before the rectum. The name sigmoid means S-shaped (see sigmoid; cf. sigmoid sinus). The walls of the sigmoid colon are muscular and contract to increase the pressure inside the colon, causing the stool to move into the rectum.
Most fish move by alternately contracting paired sets of muscles on either side of the backbone. These contractions form S-shaped curves that move down the body. As each curve reaches the back fin, backward force is applied to the water, and in conjunction with the fins, moves the fish forward. The fish's fins function like an airplane's flaps ...
It is about 5 mm thick, and is formed by an aggregation of the smooth (involuntary) circular muscle fibers of the rectum. [citation needed] The internal anal sphincter aids the sphincter ani externus to occlude the anal aperture and aids in the expulsion of the feces. Its action is entirely involuntary. It is normally in a state of continuous ...