Human Physiology: Blood, Nervous System, and Digestive Hormones

Ghrelin is a hormone released by the lining of the stomach that promotes feeding behavior. The hunger hormone ghrelin, which acts on the brain to stimulate hunger and increase food intake heightens the appeal of high calorie foods over low calorie foods. The hunger hormone ghrelin is activated by fats from the foods we eat.

Glands in the duodenum or small intestine secrete several hormones including secretin, cholecystokinin (CCK) and gastric inhibitory peptide (GIP). Secretin is a hormone secreted by the duodenal and jejunal mucosa when acid chyme enters the intestine. It stimulates secretion of pancreatic juice and to a lesser extent bile and intestinal secretion.

Lactoferrin (LF) also known as lactotransferrin (LTF) is a multifunctional protein of the transferrin family. It is a globular glycoprotein widely represented in various secretory fluids such as milk, saliva, tears and nasal secretions. It is folded into two globular units, each capable of binding up to 1.4 mg iron/g of protein. Lactoferrin is one of the components of the immune system of the body. It has antimicrobial activity (bacteriocide, fungicide) and is part of the innate defense mainly at mucoses.

Blood is salty tasty. The salt taste of blood comes from the salts, minerals and iron present in human blood. So the blood of normal persons is salty only, but it has sweet taste in some persons suffering from diabetes. As the blood of a diabetic person will contain much sugar than a normal person the blood is tasting sweety.

Red blood cells are also known as RBCs, red cells, red blood corpuscles, haematids, erythroid cells or erythrocytes. In humans mature red blood cells are oval and flexible biconcave disks. They lack a cell nucleus and most organelles to accommodate maximum space for haemoglobin. Sickle cell disease is an inherited disorder in which red blood cell is abnormally shaped. This abnormality can result in painful episodes, serious infections, chronic anemia and damage to body organs.

Macrophages are cells produced by the differentiation of monocytes in tissues. Amoeboid movement is a crawling type of movement in which the cell forms temporary cytoplasmic projections called pseudopodia (false feet) towards the front of the cell. Leukocytes like phagocytes or macrophages of the lymph show amoeboid movements to engulf antigen or microbes and to immigrate in the circulatory fluid.

They are a variety of neuroglia. Their main functions are to provide support and to insulate the axons in the central nervous system of some vertebrates. Oligodendrocytes do this by creating the myelin sheath, which is 80% lipid and 20% protein.

In this infectious disease, a specific neurotropic virus causes muscular paralysis by the destruction of the anterior horn cell or the corresponding cell of the spinal cord and medulla respectively. This disease will spread from person to person primarily via the fecal oral route.

It is the supportive tissue of the nervous system including the network of branched cells in the central nervous system (astrocytes, microglia, and oligodendrocytes) and the supporting cells of the peripheral nervous system (neurilemma and satellite cells).

The white matter on each side of the spinal cord is organised into three large areas or funiculi. Each funiculus of the spinal cord is comprised of bundles of fibers that run together and subserve the same function.

RBCs last an average of 120 days in the bloodstream. When RBCs get aged, they are removed by macrophages in the liver and spleen.

Pus is an exudate typically white-yellow, yellow or yellow-brown formed at the site of inflammation during infection. An accumulation of pus in an enclosed tissue space is known as an abscess whereas a visible collection of pus within or beneath the epidermis is known as a pustule or pimple. Neutrophils are very active in phagocytosing bacteria and are present in large amount in the pus of wounds.

Estrogens have inhibitory effect on erythropoiesis through suppression of erythropoietin production. Estrogen is the main sex hormone in women, and is essential to the menstrual cycle.

Blood group O individuals do not have either A or B antigens on the surface of their RBCs. But their blood serum contains IgM anti-A and anti-B antibodies against the A and B blood group antigens. Therefore, an individual of blood group O can receive blood only from a group O individual, but can donate blood to individuals of any ABO blood group, i.e.,  A, B, O or AB. They are known as universal donors.