Body autonomy in detail , Cheat Sheet of Pharmacology

Download Body autonomy in detail and more Cheat Sheet Pharmacology in PDF only on Docsity! 5 Cellular Studies of Human Tissues & Organ Systems UNIT 1 CELLULAR STUDIES OF HUMAN TISSUES & ORGAN SYSTEMS Structure 1.1 Introduction Objectives 1.2 Cells and Cell Structure Components of the Cell Activities of Cell 1.3 Tissue Epithelium Tissue Muscular Tissue Nervous Tissue Connective Tissue 1.4 Circulatory System 1.5 Skeletal System and Joints The Skeleton Joints: Their Composition and Movement 1.6 Summary 1.7 Terminal Questions 1.8 Answers 1.1 INTRODUCTION In this unit you will study about the composition of the human body. You will study how the cells in the body form tissues and tissues form organs and various organ form systems and the system together form the entire human body. This unit first describes the structure of the cell and the cell cycle. It also describes the important functions of the cell. This unit then describes the various types of tissues and their functions in the human body. After this, the circulatory system and the skeletal system have been described. Emphasis has been given on the general composition of these organ systems and their physiological role. Objectives After reading this unit, you should be able to: • describe the structure and function of the cells, • write about the various stages of the cell cycle, • describe the properties and functions of the four major animal tissue types in the human body; • elaborate about the architecture of the circulatory system, 6 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry • describe the various components of the circulatory system and write about their role in circulation of blood, • describe the various components of the skeletal system; and • discuss the different types of joints in the body. 1.2 CELLS AND CELL STRUCTURE The human body, on an average may have as many as 1014 cells. All cells are composed of: (i) a cell membrane which is the thin protective layer of the cell, (ii) the cytoplasm which forms the fluid of the cell, in which various structures called organelles, like the nucleus (consisting of nucleolus and chromatin network enclosed in a nuclear membrane), endoplasmic reticulum, mitochondria, lysosomes, golgi-apparatus, ribosomes, centrosomes and other cytoplasmic inclusions are suspended (Fig. 1.1a&b). (a) (b) Fig.1.1: Human cell (a) a cutaway section of the cell showing its features (b) diagrammatic representation of the cell The plasma membrane has structural and functional continuity with the elaborate membrane system consisting of nuclear membrane, endoplasmic reticulum, mitochondria, chloroplasts and the Golgi apparatus. However the plasma membrane has more cholesterol than membranes of organelles. 9 Cellular Studies of Human Tissues & Organ Systems envelope, called centrioles. Centrioles are important during the process of cell division. v) Lysosomes: These are the “suicide bags” of the cells which contain powerful hydrolytic enzymes. At the time of death of the cell the lysosome membrane ruptures, spilling out, its enzymes which results in and self-digestion (or autolysis) of the cell. vi) Mitochondria: These are known as the energy power house of the cell. They are involved in the generation of energy molecule, Adenosine triphosphate (ATP) in the cell. ATP is used for various energy dependent processes of the cell. vii) Golgi complex: It consists of 3-20 flattened membranous sacs with bulging edges, called cisterns that resemble a stack of naan bread. The cisterns are often curved, giving the Golgi complex a cuplike shape. Most cells have only one Golgi complex although some may have several. The Golgi complex is more extensive in cells that secrete proteins into the extracellular fluid. Almost all proteins secreted by the cells are glycoproteins. The main function of the golgi body is to add a carbohydrate group to the proteins manufactured by rough ER. ‘Shuttle’ vesicles containing proteins are budded off from the ER .These vesicles fuse with the cisternae at the bottom of the golgi body. The protein is quickly transferred to the series of stacked, disc-shaped, flattened membranes of the golgi body. Thus protein is transferred between the cisternae layers towards the top of the stack. The proteins as they move towards the ‘top’ of the stack are progressively converted to glycoproteins. At the top of the stack the secretory vesicles are budded off. These vesicles pass through the cytoplasm, and fuse with the cell membrane which discharges its contents to the outside (exocytosis). 1.2.2 Activities of Cell Some general activities of cells are as follows: i) Irritability: Cells have the ability to detect and respond to environmental changes. ii) Nutrition: Cells are capable of selectively absorbing fluids and dissolved substances through the cell membrane which can be used by the cell for energy, growth or repair. iii) Respiration: Cells have the ability to respire and as a result produce energy, by combining oxygen with nutrients, resulting in the formation of carbon dioxide (CO2) and water. iv) Excretion: Cells are able to discard waste materials through the cell membrane. v) Growth and Reproduction: Cells have the ability to increase in size. When cells reach the limit of their growth they are capable of dividing and so reproducing into two daughter cells. The membranes of the Golgi complex lack the ribosomes found on rough endoplasmic reticulum (ER) and so are called smooth- endoplasmic reticulum. 10 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry vi) Movement: Some cells have the ability of movement. SAQ 1 Draw a labeled diagram of human cell? 1.3 TISSUE Tissue is a collection of cells having similar origin, structure and function. A number of cells in the body carry out a particular type of work and form a particular type of tissue. There are various types of tissues in the human body. The shape of the nucleus of the cell usually corresponds to the cell form or the shape and helps to identify the type of tissue. The basic cell tissues that occur in the body are (Fig. 1.4): i) epithelial, ii) muscular, iii) nervous iv) connective. Fig.1.4: The four basic types of tissues In medicine a tissue is not like a piece of tissue paper. It is a broad term that is given to any group of cells that perform a specific function. A tissue need not form a layer. Thus, the bone marrow is also a tissue. 11 Cellular Studies of Human Tissues & Organ Systems 1.3.1 Epithelium Tissue The epithelium generally provides a covering to tissues. It covers the body surfaces and lines body cavities. The epithelium helps in protection, absorption, excretion and secretion of various substances. The main histological features common to all epithelial tissues is that: 1) The epithelial tissue consists of cells that are situated very close to each other (there is little extracellular material between epithelial cells). 2) Several types of junctional specializations unite adjacent epithelial cells (tight junctions, desmosomes and gap junctions). 3) All epithelia except for endocrine glands have one free surface, called the apical surface, which is exposed at the body surface or at the lumen (space) of the body cavity, duct, tube or vessel. 4) The lower surface of an epithelium (or basal surface) rests on a basement membrane: a non-living adhesive material secreted by the epithelium and the underlying connective tissue. 5) There are no blood vessels within the epithelial layer. 6) Epithelial cells are often characterized by frequent cell division because they are exposed to wear and tear and injury, necessitating replacement. Classification of epithelium on basis of their functions There are two basic types of epithelial tissues on basis of their function: I) Glandular epithelia that make up most of the glands in the body. II) Covering and lining epithelia form a continuous layer over all the free surfaces of the body. Classification of epithelium on basis of their cell types Epithelial tissues are classified according to the shape of the cell forming the tissue into three types, which are: i) Squamous epithelium is flattened cells ii) Cuboidal epithelium is cube-shaped cells iii) Columnar epithelium consists of elongated cells Classification of epithelium on basis of their cell layers In addition to this, the epithelium is also classified on the basis of the number of cell layers into two subtypes of epithelia: I. Simple epithelium which has only a single cell layer. II. Stratified epithelium which has more than one layer of cells 1.3.2 Muscular Tissue Muscle tissue is the excitable (able to contract and relax) tissue of the body and possesses contractile ability hence it is also called a contractile tissue Muscle Blood, cartilage, and bone are usually considered connective tissue, but because they differ so greatly from the other tissues in this class, the phrase “connective tissue proper,” is commonly used to exclude those three. 14 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry (i) cell body (ii) dendrites, and (iii) axon, as shown in Fig.1.6 and described below. i) Cell body A neuron consists of a large cell body called perikaryon or soma, that contains (i) a nucleus and (ii) cytoplasm called perikaryon. Clusters of ribosomes and rough endoplasmic called Nissl or Nissl bodies or Nissl substance are present in the cell body. These Nissl bodies are basophilic (take up basic dye) in nature. ii) Dendrites Dendrites are protoplasmic projections that arise as numerous short projections from the nerve cell body. They constitute the receptor area of the neuron and so receive the information which they transmit into (conduct input) the neuron. Dendrites thus transmit information towards the nerve cell body. Dendrites are not myelinated (Dendrites are without myelin sheath). iii) Axon The axon is a long protoplasmic process which stretches from the cell body to a distance ranging from several millimeters up to one meter. The part of the axon where it emerges from the soma is called the axon hillock. Axons transmit nerve signals away from the nerve cell body towards other nerves, muscle, or glands. Neurons usually have only one axon. Many, but not all, axons are sheathed in a multiple layer called myelin sheath. The myelin sheath functions as a kind of electrical “insulation” greatly facilitating nerve impulse transmission. The greater the amount of myelin around an axon, the faster is the rate of nerve impulse transmission. Gaps occur in the myelin sheath and are called as Nodes of Ranvier. The terminal end of the axon away from the cell body is called the terminal bouton or axon terminal or end bulb. This terminal bouton will be associated with another neuron in a synapse. Fig.1.6: Structure of a neuron Interneurons: Interneurons are the neurons between the sensory and motor neurons. 99.9% of all neurons are interneurons. The vast majority of neurons are interneurons. Interneurons are also called internuncial neurons 15 Cellular Studies of Human Tissues & Organ Systems 1.3.4 Connective Tissue Connective tissue is one of the four types of tissues in traditional classifications (the others being, epithelial, muscle, and nervous tissue). The main function of the connective tissues is to support the body and to bind or connect together all types of tissue. The connective tissue also provides a mechanical framework (the skeleton) which plays an important role in locomotion. Connective tissues consist of cells and intercellular material. Fibroblasts are the most common cell types and are responsible for producing the fibres and other intercellular materials forming the connective tissue. Other cells that occur in the connective tissue generally in the loose connective tissue are adipose cell (adipocytes), mast cells, macrophages, leucocytes, and plasma cells. The connective tissue exists in a number of forms however all types of connective tissues have three basic structural elements (Fig. 1.7): (i) cells, (ii) non-cellular fibres, and (iii) non-cellular intercellular substance (matrix or ground tissue). The types of fibres that occur in the connective tissue are: (i) collagen (collagenous) and (ii) elastic fibres and (iii) reticular fibres. Collagen fibres are for strength while the elastic ones are for elasticity of the tissue. Reticular fibers are for forming delicate structural framework. The consistency of matrix is highly variable from gelatin-like to a much more rigid material and so may be liquid (e.g. blood), semi-solid (e.g. connective tissue) or solid (e.g. bone). The other characteristic feature of all or most connective tissues is that they are: • Involved in structure and support. • Usually derived from mesoderm (middle layer of the embryonic layer). • Characterized largely by the traits of non-living tissue. Fig.1.7: A generalized structure of connective tissue showing its various components 16 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry The various types of connective tissues differ on the basis of the proportions of the cells, fibres, present in the matrix which depends on the particular nature and function of the connective tissue. Connective tissues are classified on basis of predominant fibre present into several types as you can see Fig.1.8. Fig.1.8: The various kinds of connective tissues 19 Cellular Studies of Human Tissues & Organ Systems Elastic cartilage differs from hyaline cartilage, only because of the presence of enormous amount of yellow elastic fibres in the matrix. IV) Bone Bone (osseous tissue) is a hard and rigid tissue and is the hardest amongst all the connective tissues. Bone makes up virtually the entire skeleton in adult. The bone consists of a large amount of ground substance or matrix in which living cells called osteoblasts, osteoclasts, and osteocytes are present. The matrix is impregnated with inorganic salts of calcium (45%), organic solids like ossein (35%) and water (25%). Small amounts of sodium and magnesium is also present. In addition to this, the matrix contains numerous collagenous fibres and a large amount of water. There are two types of bones: (i) compact or periesteal bones and (ii) spongy bones or cancellous bones. Long bones are the examples of compact bone. Spongy bones are present in flat bones, ends of long bones and body of the vertebrae. The compact and spongy bones differ due to the manner in which the living bone cells and matrix are arranged, resulting in the formation of two very different patterns namely (i) compact bone tissue or (ii) spongy bone tissue. i) Compact bone part Compact (dense) bone tissue consists of precise arrangements of microscopic cylindrical structures called osteons. The matrix and osteocytes of osteon are laid down in concentric rings around a central (Haversian) canal that contains blood vessels and nerve. If you look at compact bone tissue with naked eye, it looks very dense: you cannot see any cavities in it (Fig.1.9). Fig.1.9: Compact bone tissue 20 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry The compact bone as a result is hard. Its outer layer serves as an attachment for the muscles, tendons and ligaments. It has an outer fibrous layer and an inner osteogenic layer. The osteogenic layer consists of cells like the osteoblasts, osteoclasts and the osteocytes. ii) Spongy bone part In contrast to compact bone tissue, spongy (cancellous) bone consists of an irregular latticework of thin blades of bone called trabeculae. The spaces between the trabeculae contain blood vessels and bone marrow which produces blood cells (Fig.1.10). The bone marrow may be red or yellow in colour depending on the amount of fat cells. The red bone marrow produces the red blood cells. With accumulation of fat, the red bone marrow changes into the yellow bone marrow. The most important function of the bone marrow is production of RBCs, reticulo- endothelial cells, platelets, etc. The spaces between the trabeculae can be seen with naked eye and give spongy bone tissue its "spongy" look. Fig.1.10: Spongy bone tissue V) Blood Blood is a connective tissue consisting of cells separated by a liquid called the ground substance or plasma matrix or simply as plasma (Fig.1.11a). Blood is a sticky fluid connective tissue with a slightly salty taste. It is fluid present almost everywhere and is distributed by means of blood vessels: arteries, veins, arterioles, venules and capillaries. It has a bright red or scarlet colour when it flows in the arteries but a dark red or purple colour when it flows in the veins. It is slightly alkaline (pH 7.4). The plasma of the blood is a watery fluid and transports dissolved glucose, wastes, carbon dioxide and hormones. The plasma also regulates the water balance for the blood cells. Several types of cells are present in the plasma which are as follows (Fig.1.11): 21 Cellular Studies of Human Tissues & Organ Systems (a) (b) Fig.1.11: a) Components of human blood and their function (a) Non cellular components forming the plasma, b) cellular components Composition of blood Blood has of two parts (i) fluid or plasma that constitutes 55% of the blood, and (ii) suspended solid component of cells (Fig. 1.11 b) that make up upto 45% of the blood. i) Plasma The plasma (Fig. 1.11 (a)) is composed of water (90-92%) and solids (8- 10%). The solids are in turn made up of electrolytes, plasma proteins, fats, hormones, colouring substances like bile pigments, etc. The important plasma proteins are serum albumin, serum globulin and serum fibrinogen. Serum albumin and fibrinogen are derived from the liver, whereas the serum globulins are derived from lymphocytes. ii) Blood Cells The cells (Fig. 1.11 b) present in the blood are: • White Blood Corpuscles The white blood corpuscles are also called white blood cells or WBCs, or Leukocytes. These cells, unlike RBCs are nucleated (have nucleus) and do not carry the oxygen carrying pigment haemoglobin. WBC function in the immune system. The total WBC count of blood in humans is 4000-11,000/mm3. The WBCs are further subdivided, based 24 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry the white blood cells are present in it and red blood cells are absent. Lymph is thus similar in composition to blood plasma with various types of white blood cell floating in it. It flows in lymphatic vessels. SAQ 2 Fill in the blanks: i) ______________ cartilage is found in inter vertebral discs. ii) ______________ epithelium is found in the urinary bladder. iii) During _________, the cell divided into two daughter cells. iv) A ______ is the functional unit of the nervous system. v) ________ is the hardest connective tissue. 1.4 CIRCULATORY SYSTEM The circulatory system is a closed circulatory transport system responsible for the transport of nutrients, gases and waste materials through the body by means of blood. Blood as you will recall is a fluid, connective tissue that flows within a closed system of vessels, namely the arteries, veins, capillaries, etc. Blood appears as a red, viscous and slightly alkaline fluid. The total quantity of blood in the human body is approximately 5-6 litres. The important components of the circulatory system are the heart, and the blood vessels namely arteries and veins. Heart The heart is a muscular organ, lying in the upper left part of the chest (Fig. 1.14). It pumps blood through the blood vessels. The regular contractions of the heart, or when the heart pushes in, force the blood to the various parts of the body A normal heart lies under the sternum (breast bone). The heart consists of three layers (i) The outer, tough, fibrous layer or pericardium that forms a bag like structure around the heart and contains a fluid called the pericardial fluid (ii) The middle layer or the myocardium consisting of the muscular, contractile fibres and the (iii) innermost layer is called the endocardium. Internal structure of the heart: The heart is made up of four chambers, viz. two atria (singular atrium) and two ventricles. The walls of the atria are thin and serve as a filling reservoir, from which the blood is pushed into the ventricles. The ventricles are thick walled and push the blood into either the pulmonary circulation (right ventricle) or systemic circulation (left ventricle). The muscle wall surrounding the left ventricle is thicker than the wall surrounding the right ventricle due to the higher force needed to pump the blood through the systemic circulation. When the blood goes from the atria to the ventricles it goes through heart valves. When blood goes out of the ventricles it goes through valves. The valves make sure that blood only goes one way in or out. 25 Cellular Studies of Human Tissues & Organ Systems Fig.1.14: The human heart The right atrium and right ventricle of the heart receive the deoxygenated blood from various parts of the body. The deoxygenated blood going to the heart is carried in veins. The blood is carried to the right atrium by the superior vena cava and inferior vena cava. The deoxygenated blood then goes from the right atria to the right ventricle through the tricuspid valve. The blood while going from the right atrium to the right ventricle passes through the valves to make sure that blood only goes one way – from right atrium to right ventricle and prevents backflow. The right ventricle then pumps this blood to the lungs through the pulmonary (pulmonic) artery which is the only artery that carries deoxygenated blood. When blood goes out of the ventricles it goes through pulmonary semilunar valve present in the pulmonary artery. This valve also makes sure that blood only goes one way In the lungs, gas exchange takes place as the blood takes up oxygen and gives off carbon dioxide by the passive process of diffusion. Blood from the lungs goes to the left atrium through the pulmonary (pulmonic) vein which is the only vein that carries oxygenated blood. Then this oxygenated blood goes to the left atrium through the pulmonary (pulmonic) vein which is the only vein that carries oxygenated blood. Then this oxygenated blood goes to the left atrium. From the left atrium the blood goes to the left ventricle, through the 26 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry mitral valve which also prevents backward flow of blood. The left ventricle then pumps this oxygenated blood through the aortic semilunar valve to the various parts of the body by the main artery called the aorta. The aorta forks and the blood is divided between major arteries which supply the upper and lower body. The major artery divides into smaller arteries which further divides into artirios and then into capliaries. The blood thus, travels in the arteries to the smaller arterioles, then finally to the tiny capillaries which supply each cell with oxygenated blood by giving up its oxygen and taking up carbondioxide. Then the relatively deoxygenated blood travels to the venules, which coalesce into veins, then to the inferior and superior venae cavae and finally back to the right atrium where the process began. Circulatory circuits i) Pulmonary circulation: It is a short circulatory path in which venous or deoxygenated blood from the right ventricle of the heart travel in the pulmonary artery to the lungs for oxygenation. The oxygenated blood is returned to the left ventricle by the pulmonary veins. ii) Systemic circulation: The systemic circulation is concerned with transport of oxygenated blood to different tissues of the body. In this circulation the oxygenated blood originating from the left ventricle is transported by the aorta to the various tissues. The aorta then divides and subdivides to form various branches which further end into capillaries which supply the oxygenated blood to different parts of the body. The de-oxygenated blood is brought back to the heart by the inferior and superior vena-cava blood vessels, which drain into the right atrium. iii) Coronary circulation: This is the circulation of the blood to the heart tissue. The coronary arteries arise from the base of the aorta and supply the musculature and other layers of the heart. The deoxygenated blood drains into the coronary sinus and the sinus then drains into the right atrium. Autorhythmic Cells: The Conduction System The normal human heart beats continuously due to its own inherent and rhythmical electrical activity. The source of stimulation for this beating of heart is a network of specialized cardiac muscle fibres called the autorhythmic cells as these cells are self-excitable. Autorhythmic cells repeatedly generate spontaneous action potentials that trigger heart contractions. These autorhythmic cells have two important functions: (i) They act as a pacemaker, setting the rhythm for the entire heart, and (ii) they form the conduction system, the route for propagating action potentials throughout the heart muscle. The conduction system ensures that the heart chambers namely the atria and ventricles become stimulated to function as effective pumps. The electrical activity for pumping action of heart begins in a pacemaker region of the heart. Pacemaker cells are capable of spontaneous activity. The contraction of mammalian heart begins in a small piece of embryonic type muscle which forms the pacemaker. This pacemaker is located where the vena 29 Cellular Studies of Human Tissues & Organ Systems i) Tunica intima ii) Tunica media iii) Tunica adventitia Fig.1.17: A section of the artery showing its three layers 2) Veins: These are the vessels which bring blood from various parts of the body back to the right atrium of the heart. The veins almost always contain deoxygenated blood, except in the case of the pulmonary veins which carry oxygenated blood back to the heart after oxygenation from the lungs. Veins are similar to arteries but, because they transport blood at a lower pressure, they are not as strong as arteries. Walls of veins are similar to those of arteries, in that they are composed of three distinct layers though the middle layer is poorly developed. As a result, veins have thinner walls that contain less smooth muscle and less elastic tissue than arteries.Veins receive blood from the capillaries through venules after the exchange of oxygen and carbon dioxide has taken place. Venules are the microscopic vessels that continue from the capillaries and merge to form veins. Therefore, the veins transport waste-rich blood back to the lungs and heart. It is important that the waste-rich blood keeps moving in the proper direction and is not be allowed to flow backward. This is accomplished by valves that are located inside the veins and which act like gates that only allow traffic to move in one direction. Blood Pressure Blood pressure is defined as the lateral pressure exerted by the moving column of blood on the walls of the blood vessel. Blood pressure can be divided into: In medical practice the arterial blood pressure is measured in which both systolic and diastolic pressure is measured. In contrast blood pressures in the venous system, are constant and rarely exceeds 10 mm Hg. 30 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry (i) arterial blood pressure, (ii) venous blood pressure and (iii) capillary blood pressure. The blood pressure in blood vessels is traditionally expressed in millimetres of mercury (1 mmHg). Systolic blood pressure: In the arterial system, this refers to the maximum pressure during the systole (ventricular contraction) of the heart. The normal systolic blood pressure range is 110-145mmHg. Diastolic blood pressure: In the arterial system, this refers to the minimum pressure exerted during the diastole (ventricular relaxation) and ranges normally from 70-90 mmHg. Pulse pressure: The difference between the systolic and the diastolic blood pressure is called pulse pressure and its normal range is 40-55 mmHg. SAQ 3 Tick which of the following statements are true and which are false: a) The normal RBC count is 4.5 million/mm3 of blood in adult males and 5 million/mm3 in adult females. b) Human blood is composed of plasma which consists of 90-92% water and solids 8-10%. c) The normal rhythmicity of the adult human heart is 90-100/min in beats/min. d) The pulmonary vein carries the venous blood from the heart to the lungs for oxygenation. 1.5 SKELETAL SYSTEM AND JOINTS The skeleton or the osseous system forms the framework of the human body. The human skeleton is made up of 206 bones (Fig. 1.18). 1.5.1 The Skeleton The skeleton can be divided into two parts: I) The Axial skeleton: skull, vertebral column and the thoracic cage. II) Appendicular skeleton: bones of the upper and lower limbs, the scapula, the clavicle and the pelvic girdle. I) The Axial Skeleton The axial skeletal serves mainly to protect and support the internal structures of the body and consists of three main parts: 31 Cellular Studies of Human Tissues & Organ Systems Fig.1.18: The human skeleton i) The skull The skull is a large bony structure consisting of the (i) cranium, and (ii) facial bones that are attached to the cranium. The cranium is a large bony case that accommodates the brain. The skull bones consist of one occipital bone, two parietal bones, one portal bone, two temporal bones, one sphenoid bone and one ethmoid bone. All of them are joined to each other by irregular edges called sutures (Fig. 1.19). 34 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry (ii) Each upper limb (Fig. 1.21) is composed of the: a) upper arm formed of the bone called humerus. b) forearm, composed of the bones called ulna and the radius which are collectively referred to as radio-ulna. c) wrist composed of carpal bones d) palm formed by metacarpal bones and e) fingers formed by the phalanges. Fig.1.21: Bones of the upper limb ii) Lower Bones The Lower bones (Fig.1.22) are composed of the (i) pelvic girdle, and (ii) a pair of lower limbs. Fig.1.22: Bones of the lower part of body showing various parts of the hind limb and its articulation with the pelvic girdle 35 Cellular Studies of Human Tissues & Organ Systems (i) The pelvic girdle is composed of the sacrum and coccyx in the back and two hip bones on the sides. These hip bones join in the front to form the pubis symphysis (Fig. 1.23) (ii) The lower limbs: Each lower limb is formed of the: a) upper thigh bone called femur, b) patella (knee cap), c) lower part of hind limb which is below the femur and consists of two bones the (i) tibia (shin bone), and (ii) fibula. Together these bones are collectively referred to as tibio-fibula bone, d) ankle (tarsus) which is formed of the tarsals, e) intermediate region of the foot which is composed of metatarsals also called metatarsal bones and finally, f) the toes formed of the phalanges. Fig.1.23: Front view of pelvic girdle 1.5.2 Joints: Their Composition and Movement A joint is a region where two or more bones unite. The joints are classified into three types based on the composition and the degree of movement associated with each joint in the skeleton: i) Fibrous joints: The connective tissue between the bones is formed of fibrous tissue and hence the bones are not movable. The sutures of the skull bones are examples of fibrous joints. 36 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry ii) Cartilaginous joints: In this type of joint, the connective tissue is formed of hyaline cartilage and therefore the joints are slightly movable. Examples of cartilaginous joints are intervertebral discs. iii) Synovial joints: A synovial joint is a freely movable joint where the bones are not directly in contact with each other (Fig. 1.24). Fig.1.24: Synovial joint Synovial joints are further classified into the following subtypes (Fig. 1.25): Pivot joint: In this type of joint a part of one of the articulating bones fits into a groove formed in the other bone e.g. joint of the atlas and the axis (Fig. 1.25a). Ball and socket joint: In this type of joint, a ball shaped part of one bone articulates within the cavity formed by the other bone. Example of ball and socket joint are the hip joint and the shoulder joint (Fig. 1.25b). Gliding joint: In this type of joint, the articulating faces of the bones slide over each other. For example carpal joints of the wrist and the tarsal joints of the foot (Fig. 1.25c). Condyloid joint (or ellipsoidal joints): In this type of joint two bones fit together with an odd shape (e.g. an ellipse). Thus in this joint one bone is concave and the other is convex (Fig. 1.25d). Hinge joint: Here the movement is possible only in one plane, e.g. the elbow joint and knee joint (Fig. 1.25e). 39 Cellular Studies of Human Tissues & Organ Systems • The skeleton can be divided into two parts, the axial skeleton and the appendicular skeleton. • A joint is a region where two or more bones unite. • The joints of the skeleton are classified into fibrous, cartilaginous and synovial joints. 1.7 TERMINAL QUESTIONS 1. What are the important organelles present in a cell? 2. Describe the cell membrane. 3. Enumerate the different types of connective tissue. 4. What are the main functions of blood? 5. Write about the systemic and pulmonary circulation in the body. 6. Enumerate the different types of joints found in the human body. 1.8 ANSWERS Self Assessment Questions 1. Please see Fig.1.1b. 2. a) Fibrous b) Transitional c) Telophase d) Neuron e) Bone 3. a) F b) T c) F d) F 4. a) Axial b) osteons c) Ball and socket d) Humerus Terminal Questions 1. The important organelles present inside the cell are as follows: Nucleus is the structure of the living cell that governs its activities. The nucleus is surrounded by a nuclear membrane (identical to the cell membrane). The nucleus contains the chromatin (hereditary material consisting of Deoxyribose Nucleic Acid (DNA) in the form of genes. Another component of the nucleus is the nucleolus (tiny spherical structure). Endoplasmic Reticulum (ER) is an intricate system of membranes that divides the cell into its numerous compartments. ER are of two types – smooth ER and rough ER. Smooth ER is concerned with metabolism and synthesis of steroids and glycogen and rough ER is concerned with proteins synthesis. 40 Introduction to Anatomy, Physiology and Pharmaceutical Chemistry Secretory Granules store the secretory products of the cell. Centrosomes are a pair of tiny, cylindrical structures called centrioles, which are important during the process of cell division. Lysosomes are the “suicide bags” of the cells which contain powerful hydrolytic enzymes. At the time of death of the cell the lysosome membrane ruptures, their enzymes spill out, and self-digestion or autolysis of the body cells ensues. Mitochondria are known as the energy power house of the cell. These are involved in the generation of ATP in the cell which is used for various energy dependent processes in the cell. 2. Refer to subsection 1.2.1. 3. The connective tissue forms the primary binding and supporting structure between two tissues. Cells are less in number with abundant intercellular substance. The different types of connective tissue are as follows: a) Areolar connective tissue: It consists of the ground substance called matrix, within which lie two kinds of fibers (i) yellow or elastic fiber and (ii) white or collagenous fibers. These fibers intercross, thus making a network. The space within the network is occupied by the matrix and various types of cells such as fibroblasts, histiocytes, basophils, plasma cells, pigment cells, mast cells, lymphocytes, etc. b) Adipose tissue: This tissue is also known as the loose connective tissue. They are largely round in shape and contain a fatty substance within them. This stores energy in the form of fat and prevents injury to the organs. c) Reticular tissue: Even though this tissue resembles white fibrous tissue, the fibers are thinner and branching. The cells of this tissue form a part of the reticuloendothelial system in spleen, liver, bone marrow etc. d) Cartilage: This is a connective tissue that is hard but elastic in nature. It contains large quantity of matrix formed of hard substance chondrion, These are further subdivided into three types: Hyaline, Fibrous and Elastic. e) Bone: Bone is the hardest amongst all the connective tissues. It contains ground substance and bone cells. The ground substance is composed of calcium salts. There are two types of bone, compact bones and spongy bone. Long bones are the examples of compact bone. Spongy bones are present in flat bones, ends of long bones and vertebrae. Bones help in stability, protection and locomotion. They store large quantity of calcium and phosphorous and give shape to the body. The bone marrow of some bones also forms blood cells. 41 Cellular Studies of Human Tissues & Organ Systems f) Blood: It is a fluid connective tissue which is present almost everywhere and is distributed through blood vessels – arteries, veins, arterioles, venules and capillaries. The ground substance of blood is watery fluid called plasma. White blood cells or Leucocytes, red blood corpuscles or erythrocytes, and thrombocytes or platelets are suspended in it. Red blood corpuscles are non nucleated, round and double concave. White blood cells are nucleated cells of various types such as neutrophils, acidophils, basophils, monocytes and lymphocytes. Platelets are round or oval, non-nucleated bodies of varying size. g) Lymph: It is a modified fluid tissue containing 94% water and 6% solids. It differs from blood in the fact that only lymphocytes are present in it. 4. Blood is a fluid connective tissue that flows within a closed system of vessels, viz. the arteries, veins, capillaries, etc. Its general appearance is as a red, viscous and slightly alkaline fluid. The main functions of blood are: • Transport of oxygen from the lungs to the tissue and CO2 from the tissue back to the lungs. • Transport of nutrients from the digestive tract to various tissues of the body. • As a vehicle for the movement of hormones, vitamins, pigments form their source to various parts of the body. • To maintain the fluid, electrolyte and acid-base balance in the body. • To help in regulation of the body temperature. • To help in excretion of waste products formed in the cells through urine. • WBCs aid in the body’s defence mechanism against infection 5. In the body, the blood flows in two distinct closed circuits. These circuits are: i) Pulmonary circulation: It is a short circuit and arises from the right ventricle of the heart in the form of the pulmonary arteries. It carries venous blood from the heart to the lungs for oxygenation. The oxygenated blood is returned to the left ventricle by the pulmonary veins. ii) Systemic circulation: The systemic circulation is concerned with transport of blood to different tissues of the body. It originates from the left ventricle in the form of the aorta. The aorta then divided and subdivides to form various branches which further culminate into capillaries. These supply the oxygenated blood to different parts of the body. The de-oxygenated blood is brought back to the heart by the inferior and superior vena-cava, which drain into the right atrium.