The Anemias

• Anemia means a deficiency of red blood cells, which can be caused by either too rapid loss or too slow production of red blood cells. Some types of anemia and their physiological causes are the following:

Blood Loss Anemia

• After rapid hemorrhage, the body replaces the plasma within 1 to 3 days, but this leaves a low concentration of red blood cells. If a second hemorrhage does not occur, the red blood cell concentration usually returns to normal within 3 to 6 weeks.
































































• In chronic cases, a person frequently cannot absorb enough iron from the intestine to from hemoglobin as rapidly as it is lost. Red cells are then produced with too little hemoglobin inside them, giving rise to microcytic hypochromic ANEMIA.

Aplastic Anemia

• Bone marrow aplasia means lack of a functioning bone marrow. For instance a person exposed to gamma ray radiation from a nuclear bomb blast is likely to sustain complete destruction of bone marrow, followed in a few week by lethal anemia. Likewise excessive x-ray treatment, certain industrial chemicals, and given drugs to which the person might be sensitive can cause the same effect.

MEGALOBLASTIC ANEMIA

• Due to the deficiency of vitamin B12, and folic acid leads to slow reproduction of the erythroblasts in the bone marrow. As a result, these grow too large, with odd shape, and are called megaloblasts. Because the erythroblasts cannot proliferate rapidly enough to from normal numbers of red blood cells, the cells that are formed are mostly oversized, of bizarre shapes, and have fragile membranes. These cells rupture easily leaving the person in dire need of an adequate number of red cells.

HEMOLYTIC ANEMIA

• Different abnormalities of the red blood cells, many of which are hereditarily acquired, make the cells fragile, so that they rupture easily as they go through the capillaries, especially through the spleen. Even though the number of red blood cells formed is normal, or even much greater than normal in some hemolytic diseases, the red cell life span is so short that serious anemia result.
































































• Some of these types of anemia are as follows:
































































• In hereditary spherocytosis, the red cells are very small and spherical, rather than being biconcave discs. These cells cannot be compressed because they do not have the normal loose, baglike cell membrane structure of the biconcave discs. On pasing through the splenic pulp, they are easily ruptured by even slight compression.
































































• In sickle cells anemia, which is present in 0.3 to 1.0 percent of West African and American blacks, the cells contain an abnormal type of hemoglobin called hemoglobin S, caused by abnormal beta chains of the hemoglobin molecule. When this hemoglobin is exposed to low concentrations of oxygen, it precipitates into long crystals inside the red blood cell. These crystals elongate the cell and give it the appearance of being a sickle, rather than a biconcave disc. The precipitated hemoglobin also damages the cell membrane, so that the cells become highly fragile, leading to serious anemia.
































































• In erythroblastosis fetalis, antibodies from an Rh- negative mother attack Rh - positive red blood cells in the fetus. These antibodies make the cells fragile, leading to rapid rupture and causing the child to be born with serious anemia.

POLYCYTHEMIA































 

• Whenever the tissues be come hypoxic because of too little oxygen in the atmosphere, such as at high altitudes, or because of failure of delivery of oxygen to the tissues, as occurs in cardiac failure, the blood-forming organs automatically produce large quantities of red blood cells. This condition is called secondary polycythemia, and the red cell count commonly rises to 6 to 7 million/ mm3.
































































• A common type of secondary polycythemia, called physiological polycythemia, occurs in natives who live at altitudes of 14,000 to 17,000 feet. The blood count is generally 6 to 7million/ mm3; this is asociated with the ability of these people to perform high levels of continuous work even in a rarefied atmosphere.
































































• In addition to those people who have physiologic polycythemia, others have a condition known as polycythemia Vera, in which the red blood cell count may be 7to 8 million and the hematocrit 60 to 70 percent. Polycythemia vera is caused by a gene aberration that occurs in the hemocytoblastic cell line that produces the blood cells. The blast cells no longer stop producing red cells when too many cells are already present. This causes excess production of red blood cells in the same manner that a tumor of a brest causes excess production of a specific type of brest cell. It usually causes excess production of white blood cells and platelets as well.
































































• In polycythemia vera, not only does the hematocrit increases but the total blood volume also increases, rarely to almost twice normal. The viscosity of the blood in polycythemia vera sometimes increases from the normal of 3 times the viscosity of water to 10 times that of water.

LEUKOPENIA

• A condition occasionally occurs in which the bone marrow stops producing white blood cells, especially granulocytes, leaving the body unprotected against bacteria and other agents that might invade the tissue. Within two days after the bone marrow stops producing white blood cells, ulcers may appear in the mouth and colon, or the person develops some form of severe respiratory infection. Bacteria from the ulcers then rapidly invade the surrounding tissues and the blood. Without treatment death often ensues in less than a week after acute total leukopenia begins.

THE LEUKEMIAS

• Uncontrolled production of white blood cells is caused by cancerous mutation of a myelogenous or lymphogenous cell. This causes leukemia, which is usually characterized by greatly increased, numbers of abnormal white blood cells in the circulating blood.

TYPES OF LEUKEMIA

• Leukemia are divided into two general types: the lymphogenousleukemiasand the myelogenousleukemias. The lymphogenous leukemias are caused by cancerous production of lymphoid cells usually beginning in a lymph node or other lymphogenous tissue and then spreading to other areas of the body. The second type of leukemia, myelogenous leukemia, begins by cancerous production of young myelogenous cells in the bone marrow and then spreads throughout the body, so that white blood cells are produced in many extra medullary organs, especially in the lymph nodes, spleen and liver.
































































• In myelogenous leukemia, the cancerous process occasionally produces partially differentiated cells, resulting in what might be called Neutrophilic leukemia, Eosinophilic leukemia, Basophilic leukemia, or Monocytic leukemia. Leukemic cells, especially the very undifferentiated cells, are usually nonfunctional in providing the usual protection against infection asociated with white blood cells.

Hemophilia

• Hemophilia is a bleeding tendency that occurs almost exclusively in males. In 85 per cent of cases. It is caused by deficiency of Factor VIII; this type of hemophilia is called hemophilia A or clasic hemophilia. About 1 of every 10,000 males in the India has clasic hemophilia.
































































• In the other 15 per cent of the so- called hemophilia B patients, the bleeding tendency is caused by deficiency of Factor IX. Both of these factors are transmitted genetically by way of the female chromosome as a recessive trait. Therefore, almost never will a woman have hemophilia because at least one of her two X chromosomes will have the appropriate genes. If one of her X-chromosomes is deficient, she will be a hemophilia carrier, transmitting the diseases to half her male off spring and transmitted the carrier state to half her female offspring.
































































• When a person with clasic hemophilia develops severe, prolonged bleeding almost the only therapy that is truly effective is injection of purified Factor VIII. The cost of Factor VIII is high, and its availability is limited because it can be gathered only from human blood and only in extremely small quantities.

Thrombocytopenia

• Thrombocytopenia means the presence of a very law quantity of platelets in the circulatory system. People with thrombocytopenia have a tendency to bleed, as do hemophiliacs, except that the bleeding is usually from many small venules or capillaries rather than from larger vessels, as in hemophilia. As a result, small punctate hemorrhages occur throughout all the body tissues. The skin of such a person displays many small, purplish blotches, giving the disease the name thrombocytopenicpurpura.
































































• Ordinarily, bleeding does not occur untill the number of platelets in the blood fals below 50,000 per microliter rather than the normal 150,00 to 300,000. Levels as low as 10,000 per microliter are frequently lethal.

Muscular Tissue

• Muscle is one of those two tissues of animal body which have the capability to respond to a stimulus i.e., irritability.
































































• The word irritability includes two basic phenomenon in it i.e., response to a stimulus and conductivity. Here for muscles the response to stimulus means their contractile activity.
































































• Just like nerves muscles also show conductivity of stimulus as impulse but in comparison to nervous tissue it is very less. These specialized characteristics are present in a muscle due to special modification of general properties of protoplasm.
































































• The muscle cells are called myocytes or sarcocytes. These are developed from cells called myoblast. The cytoplasm of sarcocytes is called sarcoplasm and its outer covering in most of the cases is called sarcolemma.
































































• Mesodermal in origin,
































































• On the basis of gross morphological features the muscles are clasified in to the smooth or nonstriated, skeletal or striated and cardiac muscles.

(1).

Unstriped

or

smooth

or

Involuntary

-

• Unstriped or plain muscle is made up of spindle shaped cells, collected in to bundles and held together by cementing substance.
































































• These bundles are further aggregated in to large fasciculae or sheets bound by the areolar connective tissue.
































































• The cells are elongated averaging 40 to 80 in length and 6-7 in width. Each contains a single nucleus surrounded by the sarcoplasm.
































































• In the sarcoplasm the myofibrils are arranged longitudinally. There is no sarcolemma, however, the fibre is enclosed by plasma membrane.
































































• Present in alimentary canl, urinary bladder, gall bladder, spleen, trachea, eyes, skin, uterus, vagna, penis, genital ducts and blood vessels.
































































• On the basis of arrangement of muscle fibres two main types of smooth muscles occur in the human body i.e., multiunit smooth muscles and single unit smooth muscles.
































































• The single unit muscle is also called unitary muscle. These muscles are present in most of the internal organs including the wals of all hollow visceral organs. In these the fibres are arranged in bundles or sheets and are bound with gap junctions.
































































• In these type of muscles the nerve fibres terminate at the surface of the muscle. These type of muscles are myogenic in nature i.e., self excitatory. It is just because of the fact that action potential generated spontaneously within these muscles. Thus single unit muscle fibres work as a functional syncytium.
































































• In multiunit muscle the fibres are separated from each other and each fibre is innervated by a separate nerve ending. Hence, here each fibre works independently of the other.
































































• The separation of muscle fibres is done through a membrane like layer of glycoprotein.
































































• Ciliary muscles, muscles of iris in eye, muscles of nictitating membrane of lower vertebrates, arrector pili muscles of skin dermis, muscles of wals of larger blood vessels are the examples of multiunit muscles.
































































• Multiunit muscles are principally neurogenic i.e., show contraction on nervous stimulation.
































































• These muscles looks like -
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Fig. 1.17 A smooth muscle

(2).

Striped

or

Skeletal

or

Voluntary

-

• The skeletal muscle fibres are multinucleated cylindrical structures.
































































• These muscles are found to be attached with the bones and tendons and are mainly responsible for the movements of skeleton & therefore of the body.
































































• These are under the control of animal’s will & have a clear display of longitudinal and cross stariations.
































































• Muscles are in the form of bundles of individual muscle fibres. These bundles are called fasciculi. These fasciculi are covered by three coverings of connective tissue. These coverings are -
































































• Epimysium
































































• Perimycium
































































• Endomycium
































































• Epimycium is the outermost covering perimycium is the middle one and endomysium is the inner most covering. All the three coverings along with muscle fibres looks like -
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Fig. 1.18 A muscle bundle

• The transparent covering of these muscle fibres is called sarcolemma. Electron Microscopic studies suggest that it is composed of plasmalemma along with an extrinsic coat of amorphous material, similar to the basement membrane.
































































• The sarcoplasm contains other constituents as well i.e., mitochondria or sarcosomes, golgi apparatus, sarcoplasmic reticulum, lipid, glycogen, and myoglobin etc. The cytoplasm of each muscle fibre has a large number of myofibrils. These myofibrils show the presence of alternate light and dark bands over them. Each myofibril is 1 to 2 mu in diameter.
































































• The dark band is double refractive to polarized light that’s why also called anisotropic or A band. The light band is monorefractive to polarized light that’s why these are called isotropic or I band. The A band is sometimes also called Q band similarly the I band is sometimes also called J band.
































































• The I band is bisected in the middle by a dark Z line (Zwischenscheibe line) or Dobie’s line or Krause membrane. The portion between two successive Z lines is called sarcomere.
































































• The sarcomere is the contractile unit of skeletal muscles. The length of a sarcomere is about 2 to 3 mu .
































































• On careful examination of A band some dark and light areas are identified in it. The midpoint of A band is represented by a dark line called M line or M band. The M line is followed by a comparatively light zone on both the sides. This zone of both the sides along with the central M line is called H zone or H band or Hensen’s line.
































































• The rest of the portion of A band is dark in colour again and called O zone or overlapping zone. On both the sides of Z line the N line is present. This line appears as dark, thin transverse line.
































































• The above written structures in the electron micrograph of human gastronemius muscle is seen as
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Fig. 1.19 A micrograph showing different structures of skeletal muscle fibre