The Ascending Colon Is Specialized for Processing Chyme Delivered From the Terminal Ileum

Power propulsion in the terminal length of ileum may deliver relatively large volumes of chyme into the ascending colon, especially in the digestive state. Neuromuscular mechanisms analogous to adaptive relaxation in the stomach permit filling without large increases in intraluminal

Splenic

Splenic

Sigmoid Rectal Junction

^MfflRHIRHIS^ Anatomy of the large intestine. The main ^amtlt^ttttf anatomic regions of the large intestine are the ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The hepatic flexure is the boundary between the ascending and the transverse colon,- the splenic flexure is the boundary between the transverse and the descending colon. The sigmoid colon is so defined by its shape. The rectum is the most distal region. The cecum is the blind ending of the colon at the ileocecal junction. The appendix is an evolutionary vestige. Internal and external anal sphincters close the terminus of the large intestine. The longitudinal muscle layer is restricted to bundles of fibers called tenia coli.

^MfflRHIRHIS^ Anatomy of the large intestine. The main ^amtlt^ttttf anatomic regions of the large intestine are the ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The hepatic flexure is the boundary between the ascending and the transverse colon,- the splenic flexure is the boundary between the transverse and the descending colon. The sigmoid colon is so defined by its shape. The rectum is the most distal region. The cecum is the blind ending of the colon at the ileocecal junction. The appendix is an evolutionary vestige. Internal and external anal sphincters close the terminus of the large intestine. The longitudinal muscle layer is restricted to bundles of fibers called tenia coli.

pressure. Chemoreceptors and mechanoreceptors in the ce-cum and ascending colon provide feedback information for controlling delivery from the ileum, analogous to the feedback control of gastric emptying from the small intestine.

Dwell-time of material in the ascending colon is found to be short when studied with gamma scintigraphic imaging of radiolabeled markers. When radiolabeled chyme is instilled into the human cecum, half of the instilled volume empties, on average, in 87 minutes. This period is long in comparison with an equivalent length of small intestine, but it is short in comparison with the transverse colon. It suggests that the ascending colon is not the primary site for the large intestinal functions of storage, mixing, and removal of water from the feces.

The motor pattern of the ascending colon consists of orthograde or retrograde peristaltic propulsion. The significance of backward propulsion in this region is uncertain, it may be a mechanism for temporary retention of the chyme in the ascending colon. Forward propulsion in this region is probably controlled by feedback signals on the fullness of the transverse colon.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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  • jessamine
    What are the anatomical boundaries of descending colon?
    6 years ago

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