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Friday, 31 August 2018

Function of liver in digestive system




What is the liver? Describes the function of liver in digestion.


The liver, the largest organ in the mammalian body, that lies just under the diaphragm.
In the liver, millions of cells that is called hepatocytes take up nutrients that absorbed from the intestines and release them into the bloodstream. Hepatocytes perform the function the manufacture of blood proteins prothrombin and albumin.

Some major metabolic functions of the liver are given below:

1. Removal of amino acids from organic compounds.
2. Urea formation from proteins and conversion of excess amino acids into urea to decrease body levels of ammonia.
3. Manufacture of most of the plasma proteins, formation of fetal erythrocytes, destruction of worn-out erythrocytes, and synthesis of the blood-clotting agents prothrombin and fibrinogen from amino acids.
4. Synthesis of nonessential amino acids.
5. Conversion of galactose and fructose to glucose.
6. Oxidation of fatty acids.
7. Formation of lipoproteins, cholesterol, and phospholipids.
8. Conversion of carbohydrates and proteins into fat.
9. Modification of waste products, toxic drugs, and poisons.
10. Synthesis of vitamin A from carotene, and with the kidneys,
participation in the activation of vitamin D.
11. Maintenance of a stable body temperature by raising the temperature of the blood passing through it. Its many metabolic activities make the liver the major heat producer in a mammal’s body.
12. Manufacture of bile salts, which are used in the small intestine for the emulsification and absorption of simple fats, cholesterol, phospholipids, and lipoproteins.
13. Main storage center. The liver stores glucose in the form of glycogen, and with the help of insulin and enzymes, converts glycogen back into glucose as the body needs it.

 The liver also stores fat-soluble vitamins (A, D, E, and K), and minerals, such as iron, from the diet. The liver can also store fats and amino acids, and convert them into usable glucose as required.


Function of Pancreas in Digestive System




Function of the Pancreas In Digestion


The pancreas is an organ that lies ventral to the stomach and consist of both endocrine and exocrine functions.

 The function exocrine cells in the pancreas secrete digestive enzymes into the pancreatic duct, which unite with the hepatic duct from the liver to form a common bile duct that enters the duodenum. Pancreatic enzymes complete the digestion of carbohydrates and proteins and initiate the digestion of lipids. Trypsin, carboxypeptidase, and chymotrypsin digest proteins into small peptides and individual amino acids.

 Pancreatic lipases split triglycerides into smaller, absorbable glycerol and free fatty acids. Pancreatic amylase converts polysaccharides into disaccharides and monosaccharides.

The pancreas also secretes bicarbonate (HCO3) ions that help neutralize the acidic food residue coming from the stomach. Bicarbonate raises the pH from 2 to 7 for optimal digestion. Without such neutralization, pancreatic enzymes could not
function.

large intestine function in digestive system




Function of large intestine in digestion


The large intestine lack circular folds, villi, or microvilli and has the much smaller surface area. 

The small intestine joins the large intestine near a blind-ended sac, that is called
cecum.  The human cecum and its extension, the appendix, are storage sites and possibly represent evolutionary remains of a larger, functional cecum, such as is found in herbivores.

The appendix consist of greater number of lymphoid tissue and perform the function of immune system. The major functions of the large intestine contain the
reabsorption of water and minerals, and the formation and storage of feces. As peristaltic waves move food residue along, minerals diffuse or are actively transported from the residue across the epithelial surface of the large intestine into the bloodstream.

 Water follows osmotically and returns to the lymphatic system and bloodstream. When water reabsorption is insufficient, diarrhea results.
 If too much water is reabsorbed, fecal matter becomes too thick, resulting in
constipation.

Many bacteria and fungi exist symbiotically in the large intestine. They feed on the food residue and further break down its organic molecules to waste products. Then they secrete amino acids and vitamin K, which the host’s gut absorbs. But
remains
feces is a mixture of bacteria, fungi, undigested plant fiber, sloughed-off intestinal cells, and other waste products.


Sunday, 26 August 2018

Role of small intestine in Digestion




Role of small intestine in Digestion


Small intestine is the main site of digestion in which most ingested food of mammals is digested and absorbed in the small intestine.

Size of small intestine
The size human small intestine is about 4 cm in diameter and 7 to 8 m in length  It is intermediate in length between the small intestines of typical carnivores and  small intestine of herbivores of similar size, and it reflects the human’s omnivorous eating habits.
 The length of the small intestine directly relates to the total surface area available for absorbing nutrients, as determined by the many circular folds and minute projections of the inner gut surface (figure a). On the circular folds, thousands of fingerlike projections called villi. Villi  project from each square centimeter of mucosa (figure b).

Columnar epithelial cells, contain numerous microvilli, cover both the circular folds and villi (figure
c). These small projections are so dense that the inner wall of the human small intestine has a total surface area of approximately
300 m2
the size of a tennis court.


Part of small intestine
Duodenum
The first part of the small intestine, called the duodenum, functions primarily in digestion. The duodenum consist of many digestive enzymes that intestinal glands in the duodenal mucosa secrete. The pancreas secretes other enzymes. In the duodenum, digestion of carbohydrates and proteins is completed, and most lipids are digested.

Jejunum or Ileum
 The next part is the jejunum, and the last part is the ileum. Both function in nutrient absorption. The jejunum and ileum absorb the end products of digestion such as, amino acids, simple sugars, fatty acids, glycerol, nucleotides, water.
Much of this absorption involves active transport and the sodium dependent ATPase pump.

 Sugars and amino acids are absorbed into the capillaries of the villi, whereas free fatty acids enter the epithelial cells of the villi and recombine with glycerol to form triglycerides. The triglycerides are coated with proteins to form
small droplets called
chylomicrons, which enter the lacteals of the villi.

 From the lacteals, the chylomicrons move into the lymphatics and eventually into the bloodstream for transport throughout the body. Besides absorbing organic molecules, the small intestine absorbs water and dissolved mineral ions. The small intestine absorbs about 9 liters of water per day, and the large intestine absorbs the rest.

Role of stomach in mammalian digestion



Role of stomach in mammalian digestion


The mammalian stomach is a muscular, distensible sac that contain three
main functions.
(1) It stores and mixes the food bolus that received
from the esophagus.
 (2) Secretes substances such as enzymes, mucus, and hydrochloric acid [HCl] that digest the protein.
(3) Stomach also helps to control the rate at which food moves into the small
intestine through the pyloric sphincter (figure
a).
The stomach is made up of an inner mucous membrane containing thousands of gastric glands (figure
b).

Types of gastric glands

 
Parietal cells that secrete a solution that contain HCl.
 Chief cells that secrete pepsinogen, the make from the enzyme pepsin. Both of the cells are in the pits of the gastric glands.
Mucous cells
The surface of the mucous membrane at the openings of the glands contains numerous
mucous cells that secrete mucus that cover the surface of the stomach and protects it from the HCl and digestive enzymes.

Function of some hormone in stomach

 The surfaces of the upper gastrointestinal tract the esophagus and mouth have a much thinner mucous-cell layethan the stomach, which is why vomiting can cause a burning sensation in the esophagus or mouth. Endocrine cells in one part of the stomach mucosa release the hormone gastrin, which travels to target cells in the gastric glands, further stimulating them.

When the bolus of food enters the stomach, it distends the walls of the stomach. This distention, as well as the act of eating, causes the gastric pits to secrete HCl and pepsinogen. The H
ions cause pepsinogen to be converted into the active enzyme pepsin. As pepsin, mucus, and HCl mix with and begin to break down proteins, smooth mucosal muscles contract and vigorously churn and mix the food bolus.

 About three to four hours after a meal, the stomach contents have been sufficiently mixed and are a semiliquid mass called chyme .The pyloric sphincter regulates the release of the chyme into the small intestine.

Sensation of hunger pangs
When the stomach is empty, peristaltic waves cease, after about 10 hours of fasting, new waves  comes from the upper region of the stomach. These waves can cause hunger pangs as sensory nerve fibers carry impulses to the brain.

Role of Oral cavity in Mammalian Digestion




Role of Oral cavity in Mammalian Digestion

 Oral cavity is protected by the pair of lips. The lips consist of vascularized, skeletal muscle tissue which are present in sensory nerve endings. Lips help retain food in the mouth as it is being chewed and play a role in phonation. The oral cavity contains the tongue and teeth ( see figure). Mammals can mechanically process a wide range of foods because their teeth are covered with enamel (the hardest material in the body) and because their jaws and teeth exert a strong force.


The oral cavity is consist of saliva, a watery fluid that secrete by least three pairs of salivary glands. Saliva help to moistens food, binds it with mucins (glycoproteins), and forms the ingested food into a moist mass called a bolus. Saliva also contains bicarbonate ions (HCO3), which buffer chemicals in the mouth, and thiocyanate ions (SCN) and the enzyme lysozyme, which kill microorganisms. It also contributes an enzyme (amylase) necessary for the initiation of carbohydrate digestion.


Saturday, 25 August 2018

Describes the process of digestion and absorbing in mammals?




Describes the process of digestion and absorbing in mammals?


The mammalian digestion and absorbing process consist of following tract;

1. Ingestion;      The process in which mammals  are eating.
2. Peristalsis;     The involuntary muscular contractions that move ingested nutrients towards the digestive tract.
3. Segmentation
;     In these process mixing the contents in the digestive tract.
4. Secretion
;       The release of hormones, enzymes, and specific ions and chemicals that take part in digestion.
5. Digestion
;        These part involve the conversion of large nutrient particles or
molecules into small particles or molecules.
6. Absorption
;       The passage of usable nutrient molecules from
the small intestine into the bloodstream and lymphatic system for the final passage to body cells.
7. Defecation
;       The elimination from the body of undigested
and unabsorbed material as waste.

Monday, 20 August 2018

What is respiratory pigment and give their types?



What is respiratory pigment and give their types?


Respiratory pigments are organic compounds that consist of metallic copper or iron that binds oxygen. These pigments may be in form of solution within the blood or body fluids, or they may be present in specific blood cells. These pigments respond to a high oxygen concentration by combining with oxygen and to low oxygen concentrations by releasing oxygen.
 The four most common respiratory pigments are hemoglobin, hemocyanin, hemerythrin, and chlorocruorin.

Hemoglobin
Hemoglobin is a reddish pigment that contains iron that bind to oxygen.
It is the most common respiratory pigment in animals and found in all vertebrates. Hemoglobin may be carried within red blood cells or simply dissolved in the blood or coelomic fluid.

Hemocyanin
Hemocyanin contains metallic copper and has a bluish color when oxygenated, and
always occurs dissolved in hemolymph. Hemocyanin is the most commonly occurring respiratory pigment in molluscs and certain crustaceans.  Hemocyanin  release oxygen easily and to provide a ready source of oxygen to the tissues as long as concentrations of oxygen in the environment are relatively high.

Hemerythrin
Hemerythrin contains iron and is pink when oxygenated. It is nucleated cells, rather than free in body fluids or hemolymph. Sipunculans, priapulids, a few brachiopods, and some polychaetes have hemerythrin.

Chlorocruorin
Chlorocruorin also contains iron but is green when associated with low oxygen concentrations and bright red when associated with high oxygen concentrations. Chlorocruorin occurs in several families of polychaete worms.

Friday, 17 August 2018

What is THE LYMPHATIC SYSTEM and give Their Function?




THE LYMPHATIC SYSTEM


The lymphatic system of vertebrate start with small vessels called lymphatic capillaries, which are in direct contact with the extracellular fluid surrounding tissues (see fig).


The system has four major functions:
(1) To collect and drain most of the fluid that drip from the bloodstream and accumulates in the extracellular fluid,
 (2)  Small amounts of proteins is return that have left the cells.
(3) To transport lipids that have been absorbed from the small intestine.
 (4) To transport foreign particles and cellular debris to disposal centers called lymph nodes.
 The small lymphatic capillaries merge to form larger lymphatic vessels called
lymphatics.
 Lymphatics are thin-walled vessels with valves that ensure the one-way flow of lymph. Lymph is the extracellular fluid that accumulates in the lymph vessels. These vessels pass through the lymph nodes on their way back to the heart. Lymph nodes concentrate in several areas of the body and play an important role in the body’s defense against disease.



What is Blood pressure? How to measure the blood pressure in human?




What is Blood pressure? How to measure the blood pressure in human?


Ventricular contraction generates the fluid pressure, called blood pressure, that forces blood through the pulmonary and systemic circuits. More specifically, blood pressure is the force the blood exerts against the inner walls of blood vessels.

Measurement


Before the measurement we known the types of blood pressure that are given below.

Systolic pressure

The maximum pressure achieved during ventricular contraction is called the systolic pressure.

Diastolic pressure

 When the ventricles relax the pressure of arterial decrease, and  remain pressure that exit in the arteries is called the diastolic pressure.
In humans, normal systolic pressure for a young adult is about 120 mm Hg, which is the amount of pressure required to make a column of mercury (Hg) in a sphygmomanometer rise 120 mm. Diastolic pressure is approximately 80 mm Hg. Conventionally, these readings are expressed as 120/80.