Tag: role of large intestine in digestion

The caecum is an intraperitoneal pouch which is considered to be the beginning of the large intestine. It receives chyme from ileum and connects to the ascending colon of the large intestine. The caecum is called blind sac because caecum looks like a sac which has sphincter at the ileocaecal junction and it remains closed and is invisible. Hence, it is called a blind sac.

• The large intestine is the final section of the gastrointestinal tract that performs the vital task of absorbing water and vitamins while converting digested food into feces.
•  Although shorter than the small intestine in length, the large intestine is considerably thicker in diameter, thus giving it its name. 
• The large intestine is about 5 feet (1.5 m) in length and 2.5 inches (6-7 cm) in diameter.

The chyle entering the large intestine consists of about 75% water and some fatty and proteinaceous substances. Water is absorbed into the blood as the waste materials move through the colon. The symbiotic bacteria E. coli and Streptococcus faecalis normally residing in the human healthy colon, feed on protein contents of chyle, breaking them into amino acids which are absorbed into the blood. The colon bacteria also synthesize vitamin B1, B2, biotin, folic acid and K which are absorbed. They convert bile pigments into brown pigments that give colour to faeces. Intestinal bacteria also produce foul-smelling compounds and gases (methane. hydrogen sulphide) which give the characteristic odour to intestinal gas and faeces. The intestinal bacteria also help prevent pathogenic microorganisms from establishing in the intestine. 

Bartholin glands are present on both sides of vaginal opening in mammals like human females. Secretions of bartholin glands act as lubricant during sexual intercourse. Adrenal glands are important endocrine glands present over kidneys. These glands secrete adrenaline, noradrenaline hormones. Prostate is an accessory gland present in male mammals. In human males a single prostrate gland is present. The urethra runs through the center of the prostate, from the bladder to the penis, letting urine flow out of the body. In some carnivores and herbivores scent glands are present in anus. These glands secrete pheromones which act as signals to mark territory and attract possible mates.

Taenia coli are  three bands of smooth muscles which runs in the length of large intestine. Taenia coli contract lengthwise to produce the haustra, the bulges in the colon.

Large intestine is differentiated into three parts cecum, colon and rectum. Cecum continues into colon. Colon is the middle part of large intestine. The longitudinal muscle coat forms three ribbon like bands called teniae coli. Due to the presence of teniae, pouch like structure develops in lumen of colon called as haustra. The colon then continues in a uniform tube called rectum, which is the storage chamber for faeces.

Appendicitis is an inflammation of the appendix, a finger-shaped pouch that projects from the colon on the lower right of the abdomen.
Therefore, the correct answer is option B.

The inferior region of the large intestine forms a short dead-end segment known as the cecum that terminates in the vermiform appendix. The superior region forms a hollow tube known as the ascending colon that climbs along the right side of the abdomen. Just inferior to the diaphragm, the ascending colon turns about 90 degrees toward the middle of the body at the hepatic flexure and continues across the abdomen as the transverse colon. At the left side of the abdomen, the transverse colon turns about 90 degrees at the splenic flexure and runs down the left side of the abdomen as the descending colon. At the end of the descending colon, the large intestine bends slightly medially at the sigmoid flexure to form the S-shaped sigmoid colon before straightening into the rectum. The rectum is the enlarged final segment of the large intestine that terminates at the anus.

The vermiform appendix is attached to its posteromedial surface of the large intestine. It contains masses of lymphoid tissue. It is a part of mucosa-associated lymphoid tissue which gives the appendix an important role in immunity. Appendicitis is the result of a blockage that traps infectious material in the lumen. The appendix can be removed with no damage or consequence to the patient. 

Small intestine is the longest part of alimentary canal. It extends from the pylorus of the stomach to the junction between cecum and ileum. Much of digestion and absorption of food takes place in the small intestine. The small intestine is divided into three parts duodenum, jejunum and ileum