Anatomy & Physiology PDF

ANATOMY & PHYSIOLOGY 2 OBJECTIVE By the end of the course, the student will be able to describe the structure and functions of the body and its parts 3 Course outline See Ross and Wilson Anatomy and Physiology and Health and Illness, 11th Edition. 4 INTRODUCTION Anatomy: study of the structure of the body and the physical relationships involved between body parts. Physiology: study of how the parts of the body work, and the ways in which they cooperate together to maintain life and health of the individual. Pathology: study of abnormalities and how they affect body functions, often causing illness. Pathophysiology: is a convergence of pathology and physiology. It’s a discipline which explains the physiological processes or mechanisms whereby disease(pathology) develops and progresses. NB: WE SHALL BE DISCUSSING ABOUT THE NORMAL ANATOMY AND PHYSIOLOGY 5 ORGANISATION OF THE HUMAN BODY OBJECTIVES By the end of this section you will be able to: Describe the cell and its functions Describe cell multiplication Describe the transfer of substances across cell membranes Describe tissues and their functions Describe body fluids and electrolytes 6 LEVELS OF STRUCTURAL COMPLEXITY Cells: smallest independent units of living matter Can’t be seen with the naked eye, Can be microscopically distinguished by their size, shape and the dyes they absorb when stained in the laboratory. Each cell type is specialised, carries out a particular function that contributes to body needs. Cells with similar structures and functions form tissues. Different types of tissue form organs that carry out a specific function. Systems consist of a number of organs and tissues that together contribute to one or more survival needs of the body. 7 8 Levels of structural complexity Characteristics of Life Movement – change in position; motion Responsiveness – reaction to a change Growth – increase in body size; no change in shape Reproduction – production of new organisms and new cells Respiration – obtaining oxygen; removing carbon dioxide; releasing energy from foods Differentiation – unspecialized to specialized 9 Ct….. Digestion – breakdown of food substances into simpler forms Absorption – passage of substances through membranes and into body fluids Circulation – movement of substances in body fluids Assimilation – changing of absorbed substances into chemically different forms Excretion – removal of wastes produced by metabolic reactions 10 Maintenance of Life Life depends on five (5) environmental factors: Water Food Oxygen Heat Pressure 11 Requirements of Organisms Water - most abundant substance in body - required for metabolic processes - required for transport of substances - regulates body temperature Food - provides necessary nutrients - supplies energy - supplies raw materials 12 Requirements of Organisms Oxygen (gas) - one-fifth of air - used to release energy from nutrients Heat - form of energy - partly controls rate of metabolic reactions Pressure - application of force on an object - atmospheric pressure – important for breathing - hydrostatic pressure – keeps blood flowing 13 Internal environment and homeostasis External environment; surrounds the body provides the oxygen and nutrients required by all the cells of the body. Its where waste products of cellular activity are excreted into The skin provides a barrier between the dry external environment and the watery environment of most body cells. Internal environment: water-based medium in which body cells exist. Cells are bathed in fluid called interstitial or tissue fluid. Oxygen and other substances they require must pass from the internal transport systems through the interstitial fluid to reach them. Similarly, cell waste products must move through the interstitial fluid to the transport systems to be excreted. 14 A Cell membrane surrounds cells and provides a potential barrier to substances entering or leaving them. It’s semi-permeable/has selective permeability thus allowing the cell to regulate its internal composition. Smaller particles can usually pass through the membrane, some more readily than others, and therefore the chemical composition of the fluid inside is different from that outside the cell. 15 A cell with a semi-permeable membrane 16 HOMEOSTASIS Def: the maintenance of the internal environment in a fairly constant state within narrow limits. Maintained by control systems which detect and respond to changes in the internal environment. A control system has 3 basic components: detector, control centre Effector(s) Control centre: determines the limits within which the variable factor should be maintained. receives an input from the detector or sensor, integrates the incoming information. When the incoming signal indicates that an adjustment is needed the control centre responds and its output to the effector is changed. This is a dynamic process that maintains homeostasis. 17 Examples of physiological variables Temperature Water and electrolyte concentrations pH (acidity or alkalinity of body fluids Blood glucose levels Blood and tissue oxygen and carbon dioxide levels Blood pressure 18 Negative feedback mechanisms In systems controlled by negative feedback the effector response decreases or negates the effect of the original stimulus, restoring homeostasis. E.g; When body temperature falls below the preset level, this is detected by specialised temperature sensitive nerve endings. They transmit this information as an input to the hypothalamus of the brain which form the control centre. The output from the control centre activates mechanisms that raise body temperature (effectors). 19 These include: stimulation of skeletal muscles causing shivering narrowing of the blood vessels in the skin reducing the blood flow to, and heat loss from, the peripheries behavioural changes, e.g. we put on more clothes or curl up. When body temperature rises to within the normal range, the temperature sensitive nerve endings no longer stimulate the cells of the control centre and therefore the output of this centre to the effectors ceases. Most systems are controlled by negative feedback 20 Physiological negative feedback: ctrl of body temp. 21 Positive feedback mechanisms Are few The stimulus progressively increases the response, so that as long as the stimulus is continued the response is progressively being amplified (amplifier or cascade systems). E.g, blood clotting and uterine contractions during labour. During labour, contractions of the uterus are stimulated by the hormone oxytocin. These force the baby's head into the cervix of the uterus stimulating stretch receptors there. In response to this, more of the hormone oxytocin is released, further strengthening the contractions and maintaining labour. After the baby is born the stimulus (stretching of the cervix) is no longer present and the release of oxytocin stops 22 CHEMISTRY OF LIFE ATOMS, MOLECULES AND COMPOUNDS Atom: the smallest particle of an element which can exist as a stable entity. Element: a chemical substance whose atoms are all of the same type; e.g. iron contains only iron atoms. There are 92 naturally occurring elements Compounds: contain more than one type of atom; e.g, water is a compound containing both hydrogen and oxygen atoms. Body structures are made up of combinations of four elements: carbon, hydrogen, oxygen and nitrogen. Small amounts of others are present, collectively described as mineral salts 24 Atomic structure Atoms: made up of 3 main types of particles. Protons: particles present in the nucleus or central part of the atom. Each proton has one unit of positive electrical charge and one atomic mass unit. Neutrons: found in the nucleus of the atom. They have no electrical charge and one atomic mass unit. Electrons: particles which revolve in orbit around the nucleus of the atom at a distance from it. Each electron carries one unit of negative electrical charge and its mass is so small that it can be disregarded when compared with the mass of the other particles. An atom is electrically neutral; the number of positively charged protons in the nucleus is equal to the number of negatively charged electrons in orbit around the nucleus. 25 The chemistry of life depends upon the ability of the atoms to react and combine with one another to produce a wide range of molecules required for biological diversity. How does this happen? When do atoms react? Isotopes: are atoms of an element in which there is a different number of neutrons in the nucleus. This does not affect the electrical activity of these atoms because neutrons carry no electrical charge, but it does affect their atomic weight. (How do u calculate the atomic weight of such atoms?) 26 Bonds When atoms are joined together, they form a chemical bond. There are two types:- Covalent and ionic. Covalent bonds are formed when atoms share their electrons with each other. They are strong and stable. Ionic bonds are formed when electrons are transferred from one atom to another. They are usually weak. Eg. When sodium chloride is dissolved in water, the bonds breaks. Since the atoms are charged, they are no longer called atoms but ions. Positively charged ions are called cations Negatively charged ions are called anions 27 28 MOLECULES AND COMPOUNDS Molecules: consist of two or more chemically combined atoms. The atoms may be of the same element, e.g. a molecule of atmospheric oxygen (O2) consists of two oxygen atoms or contain two or more different elements; e.g. a water molecule (H2O) contains two hydrogen atoms and an oxygen atom. When two or more elements combine, the resulting molecule can also be referred to as a compound. Compounds which contain the element carbon are classified as organic, and all others as inorganic. The body contains both. When the number of electrons in the outer shell of an element is the optimum number, the element is described as inert or chemically unreactive, i.e. it will not easily combine with other elements to form compounds. These elements are the inert or noble gases —helium, neon, argon, krypton, xenon and radon. 29 ELECTROLYTES Def: An ionic compound that can conduct electricity, e.g. sodium chloride solution Electrolytes are important body constituents because: some conduct electricity, essential for muscle and nerve function some exert osmotic pressure, keeping body fluids in their own compartments some function in acid-base balance, as buffers to resist pH changes in body fluids. 30 Important electrolytes in the body a) Sodium Most abundant ion in the extra-cellular compartment. Functions. Involved in the Conduction of nerves Contraction of muscles. Regulation of acid and base balance. Acid and base balance is maintained through the exchange of hydrogen (H+) ions with sodium (Na+) ions in the kidneys. Foods rich in sodium are processed foods, snacks, smoked foods and table salt. b) Potassium Most abundant ion in the intracellular compartment. Affects nerve conduction and muscle strength. Foods rich in potassium are unripe bananas, avocados, oranges, potatoes and dates. 31 c) Calcium Makes compounds with other elements. Important constituent of bones Involved in proper nerve and muscle functioning. Acts as a co-factor in the blood clotting mechanism. Foods that are rich in calcium are grains, legumes, and leafy vegetables. d) Magnesium Normal constituent of bones. Involved in energy metabolism. Found in cocoa, seafood, dried beans and peas 32 ACIDS, ALKALIS AND pH An acid: a substance that produces hydrogen ions when dissolved. Acids act as electrolytes in water. They neutralise bases to produce salt and water. Common acids are hydrochloric acid and carbonic acid. A base: a substance that reacts with acid to form salt and water by acepting hydrogen ions and oftenly releasing hydroxyl (OH-) ions. Common bases are magnesium hydroxide and aluminium hydroxide. The balance between acids and bases must be maintained for the various processes in the body to take place optimally. 33 ACIDS, ALKALIS AND PH Number of H+ present in a solution is a measure of the acidity of the solution. Maintenance of the normal H+ concentration within the body is an important factor in maintaining homeostasis. The pH scale Def: A standard scale for the measurement of the hydrogen ion concentration in solution. Not all acids ionise completely when dissolved in water. The hydrogen ion concentration is a measure, therefore, of the amount of dissociated acid (ionised acid) rather than of the total amount of acid present. Strong acids dissociate more freely than weak acids, e.g. hydrochloric acid dissociates freely into H+ and Cl~, while carbonic acid dissociates much less freely into H+ and HCO3-. 34 Alkalinity of a solution depends on the number of hydroxyl ions (OH-). Water is a neutral solution because every molecule contains one hydrogen ion and one hydroxyl radical. For every molecule of water (H.OH) which dissociates, one hydrogen ion (H+) and one hydroxyl ion (OH-) are formed, neutralising each other. pH scale was developed taking water as the standard. In a neutral solution such as water, where the number of hydrogen ions is balanced by the same number of hydroxyl ions, the pH = 7. A pH reading below 7 indicates an acid solution, while readings above 7 indicate alkalinity. A change of one whole number on the pH scale indicates a tenfold change in [H+]. Therefore, a solution of pH 5 contains ten times as many hydrogen ions as a solution of pH 6. Ordinary litmus paper colours blue for alkalinity and red for acidity. 35 The pH scale 36 PH VALUES OF BODY FLUIDS Vary. pH value in an organ is produced by its secretion of acids or alkalis which establishes the optimum level. Body fluid pH Blood 7.35 to 7.45 Saliva 5.4 to 7.5 Gastric juice 1.5 to 3.5 Bile 6 to 8.5 Urine 4.5 to 8.0 37 Buffers Buffering mechanisms temporarily neutralize flactuations in pH thus keeping it stable within its normal limits. The lungs and the kidney are the most active organs in buffering. Lungs regulate CO2 levels in the body by either  or  breathing. Kidneys regualte pH by either  or  excretion of hydrogen and bicarbonate ions as required. Other buffer systems include body proteins and phosphate. Buffer substances/systems help maintain the Acid-Base balance so that the pH remains within normal, but narrow, limits 38 ACIDOSIS AND ALKALOSIS When the pH is below 7.35, and all the reserves of alkaline buffer are used up, the condition of acidosis exists (Acidosis is an increased acidity in the blood and other body tissue). When the reverse situation persists and the pH is above 7.45, and the increased alkali uses up all the acid reserve, the state of alkalosis exists (Alkalosis refers to a condition reducing hydrogen ion concentration of arterial blood plasma) 39 IMPORTANT BIOLOGICAL MOLECULES 1. CARBOHYDRATES Are the sugars. Composed of carbon, oxygen and hydrogen. Carbon atoms are normally arranged in a ring, with the oxygen and hydrogen atoms linked to them. When 2 sugars link up, the reaction occurring expels a molecule of water and the resulting bond is called a glycosidic linkage. Monosaccharides: Simple sugars, that can exist as single units e.g glucose, Glucose: main form in which sugar is used by cells, and blood levels are tightly controlled. Disaccharides: molecule formed when 2 monosaccharides are linked together e.g. sucrose Polysaccharides: molecule formed when more than 2 monosaccharides e.g. starch. 40 Glucose + fructose = sucrose 41 CARBOHYDRATES CT. Glucose can be broken down (metabolised) in either the presence (aerobically) or the absence (anaerobically) of oxygen, but the process is much more efficient when O2 is used. During this process, energy, water and carbon dioxide are released. This family of molecules: serves as a ready source of energy to fuel cellular activities provides a form of energy storage, e.g. glycogen forms an integral part of the structure of DNA and RNA can act as receptors on the cell surface, allowing the cell to recognise other molecules and cells. 42 2. AMINO ACIDS AND PROTEINS Amino acids contain carbon, hydrogen, oxygen and nitrogen, and many in addition carry sulphur. 20 amino acids are known to be the principal building blocks of protein. Amino acids have a basic common structure, including an amino group (NH2), a carboxyl group (COOH) and a hydrogen atom. What makes one amino acid different from the next is a variable side chain (R). When two amino acids join up the reaction expels a molecule of water and the resulting bond is called a peptide bond. 43 Amino acid structures: A. Common structure, R = variable side chain. B. Glycine, the simplest amino acid. C. Alanine. D. Phenylalanine. 44 Amino acids are sub-divided into 2 categories, essential amino acids non-essential amino acids Essential amino acids cannot be synthesised in the body, therefore they must be included in the diet. Non-essential amino acids are those which can be synthesised in the body. Nutritional value of a protein depends on the amino acids of which it is composed. 45 46 PROTEINS CT. Proteins: made from amino acids joined together are the main family of molecules from which the human body is built. Protein molecules vary enormously in size, shape, chemical constituents and function. can be used as an alternative energy source, usually in dietary inadequacy Many important groups of biologically active substances in the body are proteins, e.g.: carrier molecules, e.g. haemoglobin enzymes many hormones, e.g. insulin Antibodies 47 LIPIDS Made up of carbon, hydrogen and oxygen atoms. Strongly hydrophobic (water hating) thus they don’t mix with water: an importance in their function in the cell membrane. Groups Phospholipids, form an integral part of the cell membrane. Fat soluble vitamins (A, D, E and K) Fats (triglycerides) Prostaglandins cholesterol A molecule of fat consists of several fatty acids, all linked to a molecule of glycerol. 48 Fats are a source of energy, provide a convenient form in which to store excess calorific intake. When fats are broken down, they release energy, but the process is less efficient than when carbohydrates are used, since it requires more energy for the breakdown reaction to take place. Used in the body for: insulation protection of body parts energy storage. 49 Nucleic acids & NUCLEOTIDES Nucleic acids: large biological molecules essential for all known forms of life. They include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Nucleotides: biological molecules that form the building blocks of nucleic acids and serve to carry packets of energy within the cell e.g., ATP In the form of the nucleoside triphosphates (ATP), nucleotides play central roles in metabolism. participate in cell signaling e.g., cAMP, are incorporated into important cofactors of enzymatic reactions, e.g. coenzyme A. Nucleotides, consist of 3 subunits: a sugar unit a base one or more phosphate groups linked together. 50 DEOXYRIBONUCLEIC ACID (DNA) A double strand of nucleotides arranged in a spiral (helix) which resembles a twisted ladder. Chromosomes: clusters of DNA molecules consisting of functional subunits called genes. The nucleotides contain the sugar deoxyribose, phosphate groups and one of 4 bases: adenine [A], thymine [T], guanine [G] and cytosine [C]. A in one chain is paired with T in the other, and G with C. Nucleotides are arranged in a precisely ordered manner in which one chain is complementary to the other. DNA acts as the template for protein synthesis and is stored safely in the nucleus. 51 ENZYMES Enzymes: proteins which act as catalysts for biochemical reactions. i.e, they speed the reaction up but are not themselves changed by it, and therefore can be used over and over again. Enzymes are very selective and usually catalyse only one specific reaction. The molecule(s) entering the reaction is called the substrate and it binds to a very specific site on the enzyme, called the active site. Whilst the substrate(s) is bound to the active site the reaction proceeds, and once it is complete the product(s) of the reaction breaks away from the enzyme and the active site is ready for use again Enzymes can catalyse both synthesis and breakdown reactions, and their names (almost always!) end in ~ase. Enzyme action depends on: temperature, pH, cofactors etc. 52 Action of an enzyme: A. Enzyme and substrates. B. Enzyme-substrate complex. C. Enzyme and product. 53 MOVEMENT OF SUBSTANCES WITHIN THE BODY INTRO Nutrients absorbed in the small intestine must move to various tissues, while waste substances must travel from the tissues to their exit points from the body. Communication molecules, such as hormones, have to travel from the site of production to their destination. Water itself, the principal constituent of the body, has to move in order to be able to be distributed throughout the body fluids and keep solutes at appropriate physiological concentrations, thus maintaining homeostasis. 54 Substances will always travel from an area of high concentration to one of low concentration, assuming that there is no barrier in the way. Between two such areas, there exists a concentration gradient and movement of substances occurs down the concentration gradient, or downhill. No energy is required for such movement; this process is therefore described as passive. Where substances move uphill, i.e. against the concentration gradient; chemical energy is required, usually in the form of ATP. These processes are described as active. Passive movement of substances in the body proceeds usually in one of two main ways — diffusion or osmosis. 55 DIFFUSION Def: movement of a chemical substance from an area of high concentration to an area of low concentration. occurs mainly in gases, liquids and solutions. Process of diffusion is speeded up if the temperature rises and/or the concentration of the diffusing substance is increased. Can also occur across a semi-permeable membrane, such as the plasma membrane; in this case, only those molecules able to cross the membrane can diffuse through. E.g., the capillary wall is effectively a semi-permeable membrane; whereas water can travel freely in either direction across it, large proteins in the plasma and red blood cells are too large to cross and therefore remain in the blood. 56 57 OSMOSIS Def: the movement of water down its concentration gradient across a semi- permeable membrane. This is usually because the solute molecules are too large to pass through the pores in the membrane. The force with which this occurs is called the osmotic pressure. Water crosses the membrane down its concentration gradient from the side with the lower solute concentration the side with the greater solute concentration. This dilutes the more concentrated solution, and concentrates the more dilute solution. Osmosis proceeds until equilibrium is reached, at which point the solutions on each side of the membrane are of the same concentration and are said to be isotonic. 58 The concentration of water and solutes in the plasma is maintained within a very narrow range because if the plasma water concentration rises, i.e. the plasma becomes more dilute than the intracellular fluid within the red blood cells, then water will move down its concentration gradient across the membranes and into the red blood cells. This may cause the red blood cells to swell and burst. In this situation, the plasma is said to be hypotonic. If the plasma water concentration falls so that the plasma becomes more concentrated than the intracellular fluid within the red blood cells (the plasma becomes hypertonic), water passively moves by osmosis from the blood cells into the plasma and shrinkage of the blood cells occurs. 59 The process of osmosis. Net water movement when a red blood cell is suspended in solutions of varying concentrations (tonicity): A. Isotonic solution. B. Hypotonic solution. C. Hypertonic solution. 60 BODY FLUIDS Total body water in adults is about 60% of body weight. Extracellular water…..about 22% of body weight Intracellular water……about 38% of body weight Proportion is higher in young people and adults below average weight. It is lower in the elderly Obesity 61 Distribution of body water in a 70 kg person. 62 Importance of water 1. It makes up part of all body fluids 2. It protects cells from outside pressure 3. It helps in the regulation of body temperature 4. It maintains intracellular pressure 5. It is involved in chemical reactions 6. It washes out wastes and is, therefore, a medium of excretion 63 Extracellular Fluid (ECF) Consists of blood, plasma, lymph, cerebrospinal fluid fluid in the interstitial spaces of the body. Others (synovial fluid, pericardial fluid, pleural fluid) Interstitial or intercellular fluid (tissue fluid) bathes all the cells of the body except the outer layers of skin. It is the medium through which substances pass from blood to the body cells, and from the cells to blood. 64 INTRACELLULAR FLUID (ICF) Its composition is largely controlled by the cell itself, because there are selective uptake and discharge mechanisms present in the cell membrane. Thus, sodium levels are nearly ten times higher in the ECF than in the ICF. This concentration difference occurs because although sodium diffuses into the cell down its concentration gradient there is a pump in the membrane which selectively pumps it back out again. 65 CELLS, TISSUES AND ORGANISATION OF THE BODY THE CELL: STRUCTURE AND FUNCTIONS A cell consists of a plasma membrane organelles floating in a watery fluid called cytoplasm Organelles: small structures with highly specialised functions contained within a membrane. They include: nucleus, mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, microfilaments and microtubules. 67 SIMPLE CELL 68 69 CELL STRUCTURE AND ITS FUNCTIONS All cells in the body have a cell membrane, which forms the boundary of the cell. The cell is made of protoplasm, divided into 2: Cytoplasm: a gel-like substance in which many processes take place. Nucleus: responsible for cell coordination and cell division. It is made up of protein granules, and is surrounded by a membrane, which separates it from the cytoplasm. The cell has two different nucleic acids: The ribonucleic acid (RNA); found in the nucleus & in the cytoplasm. The deoxyribonucleic acid (DNA); found exclusively in the chromosomes (in strands of chromatin) in the nucleus. Chromosomes: the units that are involved in the transfer of the genetic material during the process of reproduction 70 PLASMA MEMBRANE Has 2 layers of phospholipids with proteins and sugar molecules embedded in them. Some proteins extend all the way through the membrane providing channels that allow the passage of electrolytes and non-lipid-soluble substances. The phospholipid molecules have a Head: is electrically charged and hydrophilic ('water loving') Tail: has no charge and is hydrophobic ('water hating'). The phospholipid bilayer is arranged like a sandwich with the hydrophilic heads aligned on the outer surfaces of the membrane and the hydrophobic tails forming a central water-repelling layer. These differences influence the transfer of substances across the membrane. 71 The membrane proteins perform several functions: Selective permeability and transport of solutes thru passive transport, active transport and group translocation Electron transport and oxidative phosphorylation. It contains enzymes and other components of the respiratory chain Excretion of hydrophilic exoenzymes and pathogenicity proteins Biosynthetic functions – it bears enzymes and carrier molecules that function in biosynthesis of DNA, cell wall polymers and membrane lipids Chemotactic systems – has receptors that attractants and repellants bind to. 72 PLASMA MEMBRANE 73 ORGANELLES a) Nucleus All cells except mature erythrocytes have a nucleus. It is the largest organelle. Contained within a membrane similar to the plasma membrane but it has tiny pores through which some substances can pass between it and the cytoplasm. Contains the body's genetic material, which directs the activities of the cell. This is built from DNA and proteins called histones coiled together forming a fine network of threads called chromatin (resemble tiny strings of beads). The DNA makes up 46 chromosomes. Within the necleus is the neucleolus which is involved in manufacture and assembly of ribosomes 74 b) Mitochondria Are membranous sausage-shaped structures in the cytoplasm. Factories for production of energy. They are involved in aerobic respiration, the processes by which chemical energy is made available in the cell. This is in the form of ATP, which releases energy when the cell breaks it down. Active cell types have largest number of mitochondria e.g. liver, muscle and spermatozoa c) Ribosomes Tiny granules composed of RNA and protein. They synthesise proteins from amino acids, using RNA as the template. When present in free units or in small clusters in the cytoplasm, the ribosomes make proteins for use within the cell. Are also found on the outer surface of nuclear envelope and rough endoplasmic reticulum where they manufacture proteins to be used outside the cell. 75 76 d) Endoplasmic reticulum (ER) A series of interconnecting membranous canals in the cytoplasm. 2 types: smooth and rough. Smooth ER synthesises lipids and steroid hormones, associated with the detoxification of some drugs. Rough ER is studded with ribosomes. These are the site of synthesis of proteins that are 'exported' (extruded) from cells, i.e. enzymes and hormones that pass out of their parent cell to be used by other cells in the body. 77 e) Golgi apparatus Consists of stacks of closely folded flattened membranous sacs involved in protein and carbohydrate processing and transfer. Present in all cells but is larger in those that synthesise and export proteins. The proteins move from the endoplasmic reticulum to the Golgi apparatus where they are 'packaged' into membrane- bound vesicles called secretory granules. The vesicles are stored and, when needed, move to the plasma membrane, through which the proteins are exported out thru exocytosis. f) Lysosomes Secretory vesicle formed by the Golgi apparatus. They contain a variety of enzymes involved in breaking down fragments of organelles and large molecules (e.g. RNA, DNA, carbohydrates, proteins) inside the cell into smaller particles that are either recycled, or extruded from the cell as waste material. 78 Lysosomes in WBCs contain enzymes that digest foreign material such as microbes. g) Cytoskeleton Microfilaments: Tiny strands of protein that provide structural support ,maintain the characteristic shape of the cell and permit cotraction. Microtubules: Contractile protein structures in the cytoplasm involved in Movement of organelles within the cell the movement of chromosomes during cell division the movement of cell extensions Centrosome: directs organization of microtubules. Consists of centrioles and are involved in cell division Cell extensions: microvilli, cilia and flagella. Have various functions. 79 CELL CYCLE Body cells get damaged, worn out and die and there4 needs to be replaced by growth and division of other similar cells. Two types of division; mitosis and meiosis Mitosis: a process that results in two new genetically identical daughter cells. Meiosis: a special division that occurs in the sex cells and results in formation of four daughter cells A typical cell cycle has two phases: Interphase and Mitosis INTERPHASE Has three phases, namely: First gap phase (G1) – cells grow in size and volume S phase – there is synthesis of DNA(through replication) Second gap phase (G2) – further growth and preparation for cell division NB:- Some cell enter a resting phase (G0) instead of continuing in the cycle. 80 MITOSIS Has four distinct stages Prophase: Replicated chromatin becomes tightly coiled. Chromatids become paired to form a chromosome unit (joined at the centromere). Mitotic apparatus (centrioles and mitotic spindle)appear and the centrioles move to either end of the cell and the nuclear envelope disappears. Metaphase: chromatids align on the centre of the spindle attached by their centromeres Anaphase: centromeres separate and each of the chromatids migrate to each end of the spindle Telophase: the mitotic spindle disappears, the chromosomes uncoil and the nuclear envelope reforms. Cytokinesis then follows where all the other organelles, cytoplasm are added by the plasma membrane splitting to form two identical cells 81 82 83 MEIOSIS Def: the process of cell division that occurs in the formation of reproductive cells (gametes — the ova and spermatozoa). The ova grow to maturity in the ovaries of the female and the spermatozoa in the testes of the male. In meiosis four daughter cells are formed after two divisions. During meiosis the pairs of chromosomes separate and one from each pair moves to opposite poles of the 'parent' cell. When it divides, each of the 'daughter' cells has only 23 chromosomes, called the haploid number. This means that when the ovum is fertilised the resultant zygote has the full complement of 46 chomosomes (the diploid number), half from the father and half from the mother. Thus the child has some characteristics inherited from the mother and some from the father. 84 Determination of sex depends upon one particular pair of chromosomes: the sex chromosomes. Females; have X chromosomes…are the same size and shape. Males; have one X chromosome and a slightly smaller Y chromosome. When the ovum is fertilised by an X-bearing spermatozoon the child is female and when it is fertilised by a Y-bearing spermatozoon the child is male. Sperm X + ovum X —> child XX = female Sperm Y + ovum X —> child XY = male 85 86 MUTATION Cells are said to mutate when their genetic make-up is altered in any way. Mutation may cause: no significant change in cell function modification of cell function that may cause physiological abnormality but does not prevent cell growth and multiplication, e.g. inborn errors of metabolism, defective blood clotting the death of the cell. Some mutations occur by chance, others may be caused by extraneous factors, such as X-rays, ultraviolet rays or some chemicals. The most important mutations are those that occur in the ova and spermatozoa. Genetic changes in these cells are passed on to subsequent generations although they do not affect the parent. 87 TRANSPORT OF SUBSTANCES ACROSS CELL MEMBRANES Passive transport: occurs when substances can cross plasma and organelle (semi- permeable) membranes and move down the concentration gradient (downhill) without using energy. a) Diffusion: process in which dissolved substances move across cells following a concentration gradient so that they balance on both sides of that gradient Small substances diffuse down the concentration gradient crossing membranes by: dissolving in the lipid part of the membrane, e.g. lipid-soluble substances: oxygen, carbon dioxide, fatty acids, steroids passing through water-filled channels, or pores in the membrane, e.g. small water-soluble substances: sodium, potassium, calcium. 88 b) Facilitated diffusion: passive process utilised by substances that are unable to diffuse through the semi-permeable membrane unaided, e.g. glucose, amino acids. Specialised protein carrier molecules in the membrane have specific sites that attract and bind substances to be transferred. The carrier then changes its shape and deposits the substance on the other side of the membrane. The carrier sites are specific and can be used by only one substance. As there are a finite number of carriers, there is a limit to the amount of a substance which can be transported at any time. This is known as the transport maximum. 89 Specialised protein carrier molecules involved in facilitated diffusion and active transport. 90 c) Osmosis: passive movement of solute materials/water from a region of higher concentration to that of lower concentration via a semi-permeable membrane. Active transport: process where energy is utilized to transport substances up their concentration gradient (uphill). Chemical energy in the form of ATP drives specialised protein carrier molecules that transport substances across the membrane in either direction. The carrier sites are specific and can be used by only one substance; thus transfer rate of substances depends on the number of sites available. 91 The sodium-potassium pump An active transport mechanism that maintains homeostasis of sodium (Na+) & potassium (K+) elctrolytes. May utilise up to 30% of the ATP required for cellular metabolism. There is a tendency for these ions to diffuse down their concentration gradients, K+ outwards and Na+ into the cell. Homeostasis is maintained as excess Na+ is pumped out across the cell membrane in exchange for K+. 92 Bulk transport Transfer of particles too large to cross cell membranes occurs by pinocytosis or phagocytosis. These particles are engulfed by extensions of the cytoplasm which enclose them, forming a membrane-bound vacuole. When the vacuole is small, pinocytosis occurs. In phagocytosis larger particles, e.g. cell fragments, foreign materials, microbes, are taken into the cell. Lysosomes then adhere to the vacuole membrane, releasing enzymes which digest the contents. Extrusion of waste material by the reverse process through the plasma membrane is called exocytosis. Secretory granules formed by the Golgi apparatus usually leave the cell in this way, as do any indigestible residues of phagocytosis. 93 Bulk transport across plasma membranes: A-E. Phagocytosis. F. Exocytosis. 94 TISSUES Are groups of cells that have a similar structure and act together to perform a specific fxn 4 main types, each of which has subdivisions. They are: epithelial tissue or epithelium connective tissue muscle tissue nervous tissue. 95 1. EPITHELIAL TISSUES Are found: covering the body lining cavities, hollow organs and tubes. In glands. Functions: protection of underlying structures from, for example, dehydration, chemical and mechanical damage secretion absorption. The cells are very closely packed and the intercellular substance,(the matrix) is minimal. The cells usually lie on a basement membrane, which is an inert connective tissue. Epithelial tissue may be: simple: a single layer of cells stratified: several layers of cells 96 A. Simple epithelium Consists of a single layer of identical cells Usually found on absorptive or secretory surfaces, where the single layer enhances these processes, and not usually on surfaces subject to stress. Types: Squamous epithelium Cuboidal epithelium Columnar epithelium The types are named according to the shape of the cells, which differs according to their functions.The more active the tissue, the taller are the cells. 97 a) Squamous (pavement) epithelium Composed of a single layer of flattened cells. The cells fit closely together like flat stones, forming a thin and very smooth membrane. Diffusion takes place freely through this thin, smooth, inactive lining of the following structures: Heart (endocardium) blood vessels endothelium lymph vessels alveoli of the lungs. Lining of collecting ducts of nephrons 98 99 b) Cuboidal (cubical) epithelium Consists of cube-shaped cells fitting closely together lying on a basement membrane. Forms the tubules of the kidneys & found in some glands. Actively involved in secretion, absorption and excretion. c) Columnar epithelium Formed by a single layer of cells, rectangular in shape, on a basement membrane. Found lining the many organs and often has adaptations suited to its functions e.g: Stomach has simple columnar epithelium Columnar epithelium in the small intestaines are lined with microvilli which increases surface area for absorption. Those in the trachea are ciliated and also have goblet cells. This produce mucus that traps dust and then the cilia removes it 100 Columnar epithelium. Ciliated columnar epithelium. 101 B. STRATIFIED EPITHELIA Consist of several layers of cells of various shapes. The superficial layers grow up from below. Basement membranes are usually absent. Main function: To protect underlying structures from mechanical wear and tear. 2 main types: stratified squamous and transitional. a) Stratified squamous epithelium Composed of a no. of layers of cells of different shapes. In the deepest layers the cells are mainly columnar and, as they grow towards the surface, they become flattened and are then shed. Keratinised stratified epithelium: Found on dry surfaces that are subjected to wear and tear, i.e. skin, hair and nails. Surface layer consists of dead epithelial cells to which the protein keratin has been added forming a tough, relatively waterproof protective layer that prevents drying of the underlying live cells. 102 Non-keratinised stratified epithelium: Found on moist surfaces that may be subjected to wear and tear but are protected from drying, e.g. the conjunctiva of the eyes, the lining of the mouth, the pharynx, the oesophagus and the vagina. b) Transitional epithelium: Composed of several layers of pear-shaped cells and is found lining the urinary bladder. Allows for stretching as the bladder fills. 103 Transitional epithelium 104 2. CONNECTIVE TISSUE Most abundant tissue in the body. The cells are more widely separated from each other than those forming the epithelium, and intercellular substance (matrix) is present in larger amounts. Fibres are usually present in the matrix, which may be of a semisolid jelly-like consistency or dense and rigid, depending upon the position and function of the tissue. Have a good blood supply. Major functions: binding and structural support protection transport insulation. 105 It is the tissue that supports body structures It is found in every part of the body. It may be loosely structured, densely structured or fatty. The different cells that will make up this type of tissue include fibroblasts, macrophages, fat cells, leucocytes plasma cells and mast cells. The most densely structured connective tissue is bone and cartilage 106 CELLS OF CONNECTIVE TISSUE CT is found in all organs supporting the specialised tissue except blood. The different types of cell involved include: Fibroblasts Fat cells Macrophages Leukocytes Plasma cells Mast cells. 107 a) Fibroblasts. large flat cells with irregular processes. Produce collagen and elastic fibres and a matrix of extracellular material. Very fine collagen fibres, called reticulin fibres, are found in very active tissue, e.g., liver and lymphoid tissue. Particularly active in tissue repair (wound healing) where they may bind together the cut surfaces of wounds or form granulation tissue following tissue destruction. 108 b) Fat cells Also known as adipocytes Occur singly or in groups Abundant especially in adipose tissue. Vary in size and fat content c) Macrophages Irregular-shaped cells with granules in the cytoplasm. Some are fixed, i.e. attached to connective tissue fibres, and others are motile. Important part of the body's defence mechanisms as they are actively phagocytic, engulfing and digesting cell debris, bacteria and other foreign bodies. Their activities are typical of those of the macrophage/ monocyte defence system, e.g. monocytes in blood, phagocytes in the alveoli of the lungs, Kupffer cells in liver sinusoids, fibroblasts in lymph nodes and spleen and microglial cells in the brain. 109 d) Leukocytes Normally found in small numbers in healthy connective tissue but migrate in significant numbers during infection when they play an important part in tissue defence. Lymphocytes synthesise and secrete specific antibodies into the blood in the presence of foreign material, e.g microbes. e) Mast cells. Similar to basophil leukocytes. Found in loose connective tissue and under the fibrous capsule of some organs, e.g. liver and spleen, and in round blood vessels. They produce granules containing heparin, histamine and other substances, which are released when the cells are damaged by disease or injury. Histamine is involved in local and general inflammatory reactions, stimulates the secretion of gastric juice is associated with the development of allergies & hypersensitivity states. Heparin prevents coagulation of blood, which may aid the passage of protective substances from blood to affected tissues. 110 Ct…. F) Plasma cells Are type of w.b.c that synthesize and secrete specific defensive antibodies They develop from B-lymphocytes Types of Connective tissues i. Loose connective tissue ii. Dense connective tissue iii. Adipose tissue iv. Lymphoid tissue v. Blood vi. Cartilage vii. Bone 111 LOOSE (AREOLAR) CONNECTIVE TISSUE Most generalised of all connective tissue. Matrix is semisolid with many fibroblasts and some fat cells, mast cells and macrophages widely separated by elastic and collagen fibres. Found in almost every part of the body providing elasticity and tensile strength. Connects and supports other tissues, e.g: under the skin between muscles supporting blood vessels and nerves in the alimentary canal in glands supporting secretory cells. 112 Loose (areolar) connective tissue. 113 ADIPOSE TISSUE Consists of fat cells (adipocytes), containing large fat globules, in a matrix of areolar tissue. 2 types: white and brown. a) White adipose tissue: Makes up 20 to 25% of body weight in well-nourished adults. Found supporting the kidneys and the eyes, between muscle fibres and under the skin, where it acts as a thermal insulator. b) Brown adipose tissue: Present in the newborn. Has a more extensive capillary network than white adipose tissue. When metabolised, it produces less energy and considerably more heat than other fat, contributing to the maintenance of body temperature. Present in only small amounts in adults. 114 Adipose tissue 115 DENSE CONNECTIVE TISSUE They contain more fibres and fewer cells than loose CT a) Fibrous tissue Made up mainly of closely packed bundles of collagen fibres with very little matrix. Fibrocytes are few in number and are found lying in rows between the bundles of fibres. Found: forming the ligaments, which bind bones together as an outer protective covering for bone (periosteum) As an outer protective covering of some organs, e.g. the kidneys, lymph nodes and the brain forming muscle sheaths (muscle fascia) which extend beyond the muscle to become the tendon that attaches the muscle to bone. 116 Fibrous tissue 117 b) Elastic tissue Capable of considerable extension and recoil. Has few cells Matrix consists mainly of masses of elastic fibres secreted by fibroblasts. Found in organs where alteration of shape is required, e.g. in large blood vessel walls, the epiglottis, the trachea and bronchi and the lungs. 118 Elastic tissue 119 LYMPHOID TISSUE A.k.a reticular tissue Has a semisolid matrix with fine branching reticulin fibres. Contains reticular cells and WBCs (monocytes and lymphocytes). Found in lymph nodes and all the organs of the lymphatic system. 120 CARTILAGE Much firmer tissue than any of the other connective tissues; the cells are called chondrocytes and are less numerous. They are embedded in matrix reinforced by collagen and elastic fibres. 3 types: hyaline cartilage fibrocartilage elastic fibrocartilage. a) Hyaline cartilage Appears as a smooth bluish-white tissue. Chondrocytes are in small groups within cell nests and the matrix is solid and smooth. Found: on the ends of long bones that form joints forming the costal cartilages, which attach the ribs to the sternum forming part of the larynx, trachea and bronchi. 121 Hyaline cartilage 122 b) Fibrocartilage Consists of dense masses of white collagen fibres in a matrix similar to that of hyaline cartilage with the cells widely dispersed. It’s a tough, slightly flexible, supporting tissue found: as pads between the bodies of the vertebrae, called the intervertebral discs between the articulating surfaces of the bones of the knee joint, called semilunar cartilages on the rim of the bony sockets of the hip and shoulder joints, deepening the cavities without restricting movement as ligaments joining bones. 123 Fibrocartilage 124 c) Elastic cartilage Flexible tissue consisting of yellow elastic fibres lying in a solid matrix. Cells (chondrocytes) lie between the fibres. Forms:- the pinna or lobe of the ear, the epiglottis part of the tunica media of blood vessel walls. 125 Elastic fibrocartilage 126 BONE Connective tissue with cells (osteocytes) surrounded by a matrix of collagen fibres that is strengthened by inorganic salts, especially calcium and phosphate. This provides bones with their characteristic strength and rigidity. 2 types: compact bone — solid or dense appearance cancellous or spongy bone — spongy or fine honeycomb appearance. 127 3. MUSCLE TISSUE Is a tissue with the capability to contract and relax thus providing movements. 3 types, consisting of specialized contractile cells: skeletal muscle smooth muscle cardiac muscle. a) Skeletal muscle tissue Described as skeletal, striated(striped) or voluntary muscle. Called voluntary because contraction is under conscious control. Cells are cylindrical in shape and may be as long as 35 cm. Each cell, commonly called a fibre, has several nuclei situated just under the sarcolemma or cell membrane of each muscle fibre. Muscle fibres lie parallel to one another and microscopically, they show well- marked transverse dark and light bands, hence the name striated or striped muscle. 128 Makes up the red part of flesh. Capable of stretching and contracting. Sarcoplasm, the cytoplasm of muscle fibres, contains: i. bundles of myofibrils, which consist of filaments of contractile proteins including actin and myosin ii. many mitochondria, which generate chemical energy (ATP) from glucose and oxygen by aerobic respiration iii. glycogen, a carbohydrate store which is broken down into glucose when required iv. myoglobin, a unique oxygen-binding protein molecule, similar to haemoglobin in red blood cells, which stores oxygen within muscle cells. 129 A myofibril has a repeating series of dark and light bands, consisting of units called sarcomeres. A sarcomere represents the smallest functional unit of a skeletal muscle fibre and consists of: thin filaments of actin thick filaments of myosin. 130 A muscle consists of a large number of muscle fibres. In addition to the sarcolemma, each fibre is enclosed in and attached to fine fibrous connective tissue called endomysium. Small bundles of fibres are enclosed in perimysium, and the whole muscle in epimysium. The fibrous tissue enclosing the fibres, the bundles and the whole muscle extends beyond the muscle fibres to become the tendon, which attaches the muscle to bone or skin. 131 b) Smooth (Visceral) Muscle Tissue Described as non-striated, visceral or involuntary. Not under conscious control and has no striations Found in the walls of hollow organs: i. regulating the diameter of blood vessels and parts of the respiratory tract ii. propelling contents of the ureters, ducts of glands and alimentary tract iii. expelling contents of the urinary bladder and ureter Microscopically, the cells are spindle shaped with only one central nucleus. No distinct sarcolemma but a very fine membrane surrounds each fibre. Bundles of fibres form sheets of muscle. 132 It also has intrinsic capability to contract and relax. This is further controlled autonomic nervous impulses, hormones and some metabolic substances 133 c) Cardiac Muscle Tissue Found exclusively in the wall of the heart. Not under conscious control but microscopically, cross-stripes characteristic of voluntary muscle can be seen. Each fibre (cell) has a nucleus and one or more branches. The ends of the cells and their branches are in very close contact with the ends and branches of adjacent cells. Microscopically these 'joints', or intercalated discs, can be seen as lines which are thicker and darker than the ordinary cross-stripes. The end-to-end continuity of cardiac muscle cells has significance in relation to the way the heart contracts. A wave of contraction spreads from cell to cell across the intercalated discs which means that cells do not need to be stimulated individually. 134 Cardiac muscle fibers 135 NOTE: Muscle functions by alternate phases of contraction and relaxation thus producing movement of body parts or the body itself. Skeletal muscle fibres are stimulated by motor nerve impulses originating in the brain or spinal cord and ending at the neuromuscular junction. Smooth and cardiac muscle have the intrinsic ability to initiate contraction. The strength of contraction, e.g. lifting a weight, depends on the number of fibres contracting at the same time. Contraction of smooth muscle is slower and more sustained than skeletal muscle. In order to contract when it is stimulated, a muscle fibre must have an adequate blood supply to provide sufficient oxygen, calcium and nutritional materials and to remove waste products. 136 Skeletal muscle tone (state of partial contraction) is essential for maintenance of posture in the sitting and standing positions. The muscle is stimulated to contract through a system of spinal reflexes. Muscle fatigue: occurs if a muscle is stimulated to contract at very frequent intervals; its response gradually becomes depressed and will in time cease. The chemical energy (ATP) which muscles require is usually derived from the breakdown (catabolism) of carbohydrate and fat. If an individual undertakes excessive exercise, the oxygen supply may be insufficient to meet the metabolic needs of the muscle fibres resulting in the accumulation of intermediate metabolic products, such as lactic acid. Where the breakdown process and the release of energy are complete, the waste products are carbon dioxide and water. 137 Each skeletal muscle consists of a fleshy part made up of striped fibres and tendinous parts consisting of fibrous tissue, usually at both ends of the fleshy part. The muscle is attached to bone or skin by these tendons. When the tendinous attachment of a muscle is broad and flat it is called an aponeurosis. To be able to produce movement at a joint, a muscle or its tendon must stretch across the joint. The muscles of the skeleton are arranged in groups, some of which are antagonistic to each other. To produce movement at a joint, one muscle or group of muscles contracts while the antagonists relax; e.g. to bend the knee the muscles on the back of the thigh contract and those on the front relax. 138 NERVOUS TISSUE 2 types of tissue: i. Excitable cells — called neurones; they initiate, receive, conduct and transmit information. ii. Non-excitable cells (glial cells)— support the neurones. NB: TO BE DISCUSSED IN LATER SESSIONS 139 Dendrite nucleus Axon hillock axon Axon collateral Axon terminal (synaptic button) 140 A neuron TISSUE REGENERATION Extent of regeneration depends on the normal rate of physiological turnover of particular types of cell. Those with a rapid turnover regenerate most effectively. 3 categories: a) Labile cells: Cells in which replication is normally a continuous process. Include cells in: epithelium of e.g. skin, mucous membrane, secretory glands, ducts, uterus lining bone marrow blood spleen and lymphoid tissue. 141 b) Stable cells: Cells that have retained the ability to replicate but do so infrequently. Include: liver, kidney and pancreatic cells fibroblasts smooth muscle cells osteoblasts and osteoclasts in bone. c) Permanent cells: Cells that are unable to replicate after normal growth is complete. Include: nerve cells (neurones) skeletal and cardiac muscle. 142 MEMBRANES Def: sheets of epithelial tissue and their supporting connective tissue that cover or line internal structures or cavities. Main membranes are: i. Mucous ii. Serous iii.Synovial iv.Cutaneous 143 a) Mucous membrane Moist lining of the alimentary, respiratory and genitourinary tracts; known as the mucosa. Consists of epithelial cells, some of which produce a secretion called mucus, a slimy tenacious fluid. As the cells fill up with mucus they have the appearance of a goblet or flask and are known as goblet cells. They mucus is then released to the surface when the cell bursts Organs lined by mucous membrane have a moist slippery surface. Mucus protects the lining membrane from drying, and mechanical and chemical injury. In the respiratory tract it traps inhaled foreign particles, preventing them from entering the alveoli of the lungs. 144 b) Serous membrane Also called serosa; secrete serous watery fluid. Consist of a double layer of loose areolar connective tissue lined by simple squamous epithelium. The parietal layer lines a cavity and the visceral layer surrounds organs within the cavity. The 2 layers are separated by serous fluid secreted by the epithelium. Found lining cavities and organs i.e. sites like i. The pleura; lining the thoracic cavity and surrounding the lungs ii. The pericardium; lining the pericardial cavity and surrounding the heart iii. The peritoneum; lining the abdominal cavity and surrounding abdominal organs. The serous fluid between the visceral and parietal layers enables an organ to glide freely within the cavity without being damaged by friction between it and adjacent organs. 145 c) Synovial membrane Found lining the joint cavities and surrounding tendons, which could be injured by rubbing against bones, e.g. over the wrist joint. Made up of a layer of fine, flattened epithelial cells on a layer of delicate connective tissue (areolar CT and elastic fibres). Secretes clear, sticky, oily synovial fluid, which acts as a lubricant to the joints and helps to maintain their stability. 146 GLANDS Def: groups of epithelial cells which produce specialised secretions. Types Exocrine glands: glands that discharge their secretion on to the epithelial surface of an organ, either directly or through a duct. Vary in size, shape and complexity. Secrete mucus, saliva, digestive juices and earwax. Endocrine (ductless) glands: glands that discharge their secretions into blood and lymph; secrete hormones. 147 148 Exocrine glands: A. Simple glands. B. Compound (branching) glands. ORGANISATION OF THE BODY ANATOMICAL TERMS Anatomical position: The body is in the upright position with the head facing forward, the arms at the sides with the palms of the hands facing forward and the feet together. Anatomical Plane - An imaginary surface formed by extension through any axis of the body or through two definite points on the body. 150 Anatomical position 151 152 Anatomical planes Coronal (frontal or lateral) Plane - Plane running from left to right, dividing the body into a front and back portion. Sagittal (anterior-posterior) Plane - Plane that runs from front to back, cutting the body into a right and a left part. Parasagittal Plane: Sagittal plane that divides the body into unequal right and left regions. Midsagittal (median) Plane - Plane passing longitudinally through the middle of the body from front to back, dividing it into right and left halves. Transverse - Plane that runs across the body, dividing it into a top and bottom portion; also known as the horizontal plane. 153 154 155 156 Movement in Planes and Axis of Rotation Describing Position and Movement A body movement can be described in terms of the anatomical plane through which it occurs and the anatomical axis around which it rotates. The GENERAL RULE: The axis of rotation is perpendicular to the plane of movement. 158 Anatomical Axis Anatomical Axis: Axis are used to describe how rotation of the muscles and bones take place. Longitudinal or polar axis: is in a “north-south” relationship to the anatomical position. Horizontal or bilateral axis: is in an “east-west” relationship to the anatomical position. Antero-posterior axis: is in a “front-to-back” relationship to the anatomical position. 159 160 Terms of relative position and direction (6 pairs) Lateral: is away from or further from the midline Medial: is towards or closer to the midline Proximal: Closer to the trunk or point of attachment; top of limb segment. Distal: Away from the trunk or point of attachment; bottom of limb segment Anterior: (ventral) Towards the front of the body Posterior: (dorsal) Towards the back of the body 161 Ct… Superior: Towards the top of the body Inferior: Towards the bottom of the body Deep: Farther away from the surface of the body Superficial: Closer to the surface of the body Plantar: Towards the sole of the foot Dorsum: Uppermost surface of the foot 162 Movt. in sagittal plane Flexion: Decreasing angles between two segments Extension: Increasing angles between two segments Hyperextension: Increasing angles more than 180° Major Joints involved : Wrist, Elbow, Shoulder, Hip, Knee, Trunk, Neck, & Ankle 163 Movt. In frontal plane Abduction : Away from midline Adduction: Closer to midline Radial/Ulnar deviation Inversion/Eversion Lateral flexion to R/L Elevation/Depression Upward/Downward rotation Major Joints involved :Shoulder, Hip, Wrist, Ankle, Trunk, Neck, & Scapula 164 Movt. on transverse plane External/Internal rotation Horizontal abduction/adduction Pronation: Palm down Supination: Palm up Rotation to R/L Protraction/Retraction** Major joints involved: Hip, Shoulder, Radioulnar, Neck,Trunk, & Scapula** 165 Helpful Hints…. Axis of rotation is always perpendicular to the plane of movement. In the anatomical position, all flexion/extension occurs in the sagittal plane, all abduction/adduction occurs in the frontal plane, and all rotation occurs in the transverse plane. More involved movements are usually not in one specific plane but occur as a combination of motions from more than one plane e.g. circumduction of the shoulder joint. 166 167 THE SKELETON Bony framework of the body. Forms the cavities and fossae that protect some structures, forms the joints and gives attachment to muscles. Made up of 206 bones Accounts for approx 14% of the body weight Functions of the skeletal system: Supports tissues and provides a framework for our body. Protects organs e.g. rib cage, skull Reservoir of minerals such as phosphorus and calcium which may be used in time of need (repair and function). Produces Red & white blood cells & platelets. Provides the levers on which muscles pull to produce movement. 168 Divided into 2 parts: axial and appendicular Axial skeleton (axis of the body) consists of: skull vertebral column sternum or breast bone ribs. Appendicular skeleton (appendages attached to the axis of the body) consists of: the bones of the upper limbs, the two clavicles and the two scapulae the bones of the lower limbs and the two innominate bones of the pelvis. 169 170 AXIAL SKELETON 1. Skull 2 parts, the cranium, which contains the brain the face. Consists of a number of bones which develop separately but fuse together as they mature. The only movable bone is the mandible or lower jaw. 171 Functions of the skull 1) Protection of the delicate structures of the brain, eyes and inner ears 2) Maintaining patency of the nasal passages enabling breathing 3) Eating – movement of the mandible allows chewing NB: various parts of the skull have specific functions 172 2. vertebral column Consists of 24 movable bones (vertebrae) plus the sacrum and coccyx. The bodies of the bones are separated from each other by intervertebral discs, consisting of cartilage. Has 5 parts and the bones of each part are numbered from above downwards. 7 cervical 12 thoracic 5 lumbar 1 sacrum (5 fused bones) 1 coccyx (4 fused bones 173 The first cervical vertebra, called the atlas, articulates with the skull. Thereafter each vertebra forms a joint with the vertebrae immediately above and below. In the cervical and lumbar regions more movement is possible than in the thoracic region. The sacrum consists of five vertebrae fused into one bone which articulates with the fifth lumbar vertebra above, the coccyx below and an innominate (pelvic or hip) bone at each side. The coccyx consists of the four terminal vertebrae fused into a small triangular bone which articulates with the sacrum above. 174 175 Functions of vertebral column 1. Protects the spinal cord. In each bone there is a hole or foramen (vertebral foramen) and collectively form a canal where the spinal cord lies. 2. Adjacent vertebrae form openings (intervertebral foramina) through which spinal nerves pass from the spinal cord to all parts of the body. 3. Articulates with ribs in the thoracic region forming joints which move during respiration. Intervetebral foramina 176 3. Thoracic cage The thoracic cage is formed by: 12 thoracic vertebrae 12 pairs of ribs 1 sternum or breast bone. 177 Functions of the thoracic cage 1. Protects the thoracic organs e.g the heart, lungs, large blood vessels and other structures. 2. Forms joints between the upper limbs and the axial skeleton. The upper part of the sternum, the manubrium, articulates with the clavicles forming the only joints between the upper limbs and the axial skeleton. 3. Gives attachment to the muscles of respiration: — intercostal muscles occupy the spaces between the ribs and when they contract the ribs move upwards and outwards, increasing the capacity of the thoracic cage, and inspiration (breathing in) occurs. — the diaphragm is a dome-shaped muscle which separates the thoracic and abdominal cavities. It is attached to the bones of the thorax and when it contracts it assists with inspiration. 4. Enables breathing (ventilation) to take place. 178 APPENDICULAR SKELETON The appendages are: the upper limbs and the shoulder girdles the lower limbs and the pelvic girdle A shoulder girdle is composed of a clavicle and a scapula The pelvic girdle is composed of the two innominate bones and the sacrum. 179 Functions of appendicular skeleton 1. Voluntary movement. The bones, muscles and joints of the limbs are involved in voluntary movement; ranging from very fine movements to coordinated movements. 2. Protection of delicate structures such as blood vessels and nerves that lie along the length of bones of the limbs (by the muscles and skin). 180 CAVITIES OF THE BODY 4 cavities: cranial thoracic abdominal pelvic. 181 a) Cranial cavity Contains the brain Boundaries formed by the bones of the skull: Anteriorly — 1 frontal bone Laterally — 2 temporal bones Posteriorly — I occipital bone Superiorly — 2 parietal bones Inferiorly — 1 sphenoid and 1 ethmoid bone and parts of the frontal, temporal and occipital bones. 182 183 b) Thoracic cavity Situated in the upper part of the trunk. Boundaries formed by a bony framework and supporting muscles : Anteriorly — the sternum and costal cartilages of the ribs Laterally — 12 pairs of ribs and the intercostal muscles Posteriorly — the thoracic vertebrae and the intervertebral discs between the bodies of the vertebrae Superiorly — the structures forming the root of the neck Inferiorly — the diaphragm, a dome-shaped muscle. 184 Contents of thoracic cavity 1. the trachea, 2 bronchi, 2 lungs 2. the heart, aorta, superior and inferior vena cava, numerous other blood vessels 3. the oesophagus 4. lymph vessels and lymph nodes 5. nerves. The mediastinum: refers to the space between the lungs including the structures found there, such as the heart, oesophagus and blood vessels. 185 186 Mediastinum Superior thoracic aperture 187 c) Abdominal cavity Largest cavity in the body. It’s oval in shape Situated in the main part of the trunk and its boundaries are: Superiorly — the diaphragm, which separates it from the thoracic cavity Anteriorly — the muscles forming the anterior abdominal wall Posteriorly —the lumbar vertebrae and muscles forming the posterior abdominal wall Laterally — the lower ribs and parts of the muscles of the abdominal wall Inferiorly — the pelvic cavity with which it is continuous. To facilitate the description of the positions of the organs and structures it contains, the abdominal cavity is divided into the nine regions. 188 Regions of abdominal cavity 189 Contents of abdominal cavity Organs and glands involved in the digestion and absorption of food. These are: the stomach, small intestine and most of the large intestine the liver, gall bladder, bile ducts and pancreas. Other structures include: the spleen 2 kidneys and the upper part of the ureters 2 adrenal (suprarenal) glands numerous blood vessels, lymph vessels, nerves lymph nodes. 190 191 Organs occupying anterior part of abdominal cavity abdominal organs occupying the posterior part of the abdominal 192 cavity d) Pelvic cavity Roughly funnel shaped and extends from the lower end of the abdominal cavity. Boundaries are: Superiorly — continuous with the abdominal cavity Anteriorly — the pubic bones Posteriorly — the sacrum and coccyx Laterally — the innominate bones Inferiorly — the muscles of the pelvic floor. 193 Contents of pelvic cavity a) sigmoid colon, rectum and anus b) some loops of the small intestine c) urinary bladder, lower parts of the ureters and the urethra d) in the female, the organs of the reproductive system: the uterus, uterine tubes, ovaries and vagina. e) in the male, some of the organs of the reproductive system: the prostate gland, seminal vesicles, spermatic cords, deferent ducts (vas deferens), ejaculatory ducts and the urethra (common to the reproductive and urinary systems) 194 Female reproductive organs 195 196 Male reproductive organs THE BLOOD Blood is a connective tissue. Provides means of communication between the cells of different parts of the body. Carries: a) oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs for excretion b) nutrients from the alimentary tract to the tissues and cell wastes to the excretory organs, principally the kidneys c) hormones secreted by endocrine glands to their target glands and tissues d) heat produced in active tissues to other less active tissues e) protective substances, e.g. antibodies, to areas of infection f) clotting factors that coagulate blood, minimising its 198 Blood makes up about 7% of body weight (about 5.6 litres in a 70 kg man). Proportion is less in women & greater in children, gradually decreasing until the adult level is reached. Blood in the blood vessels is in continual flow to maintain a fairly constant environment for the body cells. Blood volume and the concentration of its many constituents are kept within narrow limits by homeostatic mechanisms. 199 COMPOSITION OF BLOOD Composed of a straw-coloured transparent fluid, plasma, in which different types of cells are suspended. Composition Plasma constitutes about 55% Cells about 45% of blood volume 200 PLASMA Constituents are water (90 to 92%) and dissolved substances, including: plasma proteins: albumins, globulins (including antibodies), fibrinogen, clotting factors inorganic salts (mineral salts): sodium chloride, sodium bicarbonate, potassium, magnesium, phosphate, iron, calcium, copper, iodine, cobalt nutrients, principally from digested foods, e.g. glucose, amino acids, fatty acids, glycerol and vitamins waste materials, e.g. urea, uric acid, creatinine hormones enzymes, e.g. certain clotting factors gases, e.g. oxygen, carbon dioxide, nitrogen. 201 Plasma proteins Make up about 7% of plasma Normally retained within the blood, because they are too big to escape through the capillary pores into the tissues. Largely responsible for creating the osmotic pressure of blood which keeps plasma fluid within the circulation. If plasma protein levels fall, because of either reduced production or loss from the blood vessels, osmotic pressure is also reduced, and fluid moves into the tissues (oedema) and body cavities. They are mainly formed in the liver and are responsible for the viscosity of plasma (mainly albumin and fibrinogen) Examples: albumins, globulins (including antibodies), 202 a) Albumins: Most abundant plasma proteins Functions Maintain a normal plasma osmotic pressure (main). Act as carrier molecules for lipids and steroid hormones. b) Globulins: Main functions include: Act as Antibodies (immunoglobulins), which are complex proteins produced by lymphocytes that play an important part in immunity. They bind to, and neutralise, foreign materials (antigens) such as micro-organisms. transportation of some hormones and mineral salts; e.g. thyroglobulin carries the hormone thyroxine and transferrin carries the mineral iron inhibition of some proteolytic enzymes, e.g. 2 macroglobulin inhibits trypsin activity. 203 c) Clotting factors: substances essential for coagulation of blood. D). Fibrinogen: Synthesised in the liver and is essential for blood coagulation. Serum: plasma from which clotting factors have been removed. Plasma viscosity (thickness) is due to plasma proteins, mainly albumin and fibrinogen. Viscosity is used as a measure of the body's response to some diseases. 204 Inorganic salts (mineral salts) (Electrolytes) Involved in Cell formation, contraction of muscles, transmission of nerve impulses, formation of secretions maintenance of the balance between acids and alkalis. 205 Nutrients Food is digested in the alimentary tract and the resultant nutrients e.g. monosaccharides, amino acids, fatty acids, glycerol and vitamins, are absorbed. Together with mineral salts they are required by all body cells to provide energy and heat, Provide materials for repair and replacement, Pprovide for the synthesis of other blood components and body secretions. Organic waste products Urea, creatinine and uric acid are the waste products of protein metabolism. They are formed in the liver and conveyed in blood to the kidneys for excretion. Carbon dioxide, released by all cells, is conveyed to the lungs for excretion. 206 Hormones Def: Chemical compounds synthesised by endocrine glands. They pass directly from the cells of the glands into the blood which transports them to their target tissues and organs elsewhere in the body, where they influence cellular activity. Gases Oxygen, carbon dioxide and nitrogen are transported round the body in solution in plasma. Oxygen and carbon dioxide are also transported in combination with haemoglobin in red blood cells. Most oxygen is carried in combination with haemoglobin and most carbon dioxide as bicarbonate ions dissolved in plasma. 207 CELLULAR CONTENT OF BLOOD 3 types of blood cells. erythrocytes or red cells thrombocytes or platelets leukocytes or white cells. All blood cells originate from pluripotent stem cells and go through several developmental stages before entering the blood. Haemopoiesis: process of blood cell formation; takes place within red bone marrow. For the first few years of life, red marrow occupies the entire bone capacity and, over the next 20 years, is gradually replaced by fatty yellow marrow that has no erythropoietic function. In adults, hemopoiesis is confined to flat bones, irregular 208 HAEMOPOIESIS 209 ERYTHROCYTES (Red Blood Cells) Circular biconcave non-nucleated discs with a diameter of about 7 micrometers whose main function is transport of gases Characteristics (adaptations) of the R.B.C They are biconcave – to  S.A for gaseous exchange They have a thin central portion – to allow fast entry and exit of gases They are flexible – so that they can squeeze thru narrow capillaries Contain no organelles – thus creating more room for Hb 210 r.b.c counts 1) Erythrocyte count: number of erythrocytes per litre (1) or per cubic millimetre (mm3) of blood. 2) Packed cell volume (PCV)or haematocrit: volume of red cells in 1 litre or 1 mm3 of whole blood. 3) Mean cell volume(MCV): average-15volume of cells, measured in femtolitres (fl = 101 litre). 4) Haemoglobin: weight of haemoglobin in whole blood, measured in grams per 100 ml. 5) Mean cell haemoglobin(MCH): average amount of haemoglobin -12 in each cell, measured in picograms (pg = 101 gram). 6) Mean cell haemoglobin concentration(MCHC): amount of haemoglobin in 100 ml of red cells. 211 212 assignment Make notes on Haemopoiesis: stages in development of blood cells (include the diagram on differentiation) Normal values of cellular elements in human blood 213 Development and lifespan of erythrocytes Formed in red bone marrow, which is present in the ends of long bones and in flat and irregular bones. Life span in the circulation is about 120 days Process of development of red blood cells from pluripotent stem cells takes about 7 days and is called erythropoiesis. It is characterised by two main features: Pluripotent stem cell maturation of the cell formation of haemoglobin inside the cell MATURATION 214 a) Maturation of the cell: During this process the cell decreases in size and loses its nucleus. These changes depend on the presence of vitamin B12 and folic acid. These are present in sufficient quantity in a normal diet containing dairy products, meat and green vegetables; excess is stored in the liver. Absorption of vitamin B12 depends on a glycoprotein called intrinsic factor secreted by parietal cells in the gastric glands. Together they form the intrinsic factor-vitamin B12 complex (IF-B12). During its passage through the intestines, the bound vitamin is protected from enzymatic digestion, and is absorbed in the terminal ileum. Folic acid is absorbed in the duodenum and jejunum where it undergoes change before entering the blood. Deficiency of either vitamin B12 or folic acid leads to impaired red cell production. 215 Maturation of the erythrocyte 216 b) Formation of haemoglobin. Hb is a complex protein, consisting of globin and an iron- containing substance called haem, and is synthesised inside developing erythrocytes in red bone marrow. Hb in mature erythrocytes combines with oxygen to form oxyhaemoglobin, giving arterial blood its characteristic red colour. Hb is also involved, to a lesser extent, in the transport of carbon dioxide from the body cells to the lungs for excretion. Each Hb molecule contains four atoms of iron. Each atom can carry one molecule of oxygen, therefore one Hb molecule can carry up to four molecules of oxygen. Haemoglobin is said to be saturated when all its available binding sites for oxygen are filled. When oxygen levels are low, only partial saturation is possible. 217 Haemoglobin binds reversibly to oxygen to form Oxyhaemoglobin Oxygen presence in blood changes the colour of blood. Blood rich on oxygen is bright red while blood low in oxygen is dark bluish in colour coz its not saturated. Factors which increases release of oxygen from oxyhaemoglobin includes:- Low pH Low levels of oxygen in blood (hypoxia) Temperature 218 Control of erythropoiesis Through homeostatic negative feedback mechanism; the bone marrow produces erythrocytes at the rate at which they are destroyed. Primary stimulus to increased erythropoiesis is hypoxia which occurs when: oxygen-carrying power of blood is reduced by e.g. haemorrhage or excessive erythrocyte breakdown (haemolysis) due to disease oxygen tension in the air is reduced, as at high altitudes. Hypoxia increases erythrocyte formation by stimulating the production of the hormone erythropoietin, mainly by the kidneys. 219 Effects of Control of erythropoiesis erythropoietin Increases production of proerythrocytes Speeds up reticulocyte maturation And this  oxygen carrying capacity of blood and thus  hypoxia. When erythropoietin levels are low, red cell formation does not take place even in the presence of hypoxia, and anaemia develops. 220 Destruction of erythrocytes Life span of erythrocytes is about 120 days Their breakdown/haemolysis, is by phagocytic reticuloendothelial cells found mainly in the spleen, bone marrow and liver. As erythrocytes age, changes in their cell membranes make them more susceptible to haemolysis (membranes become fragile). Iron released by haemolysis is retained in the body and reused in the bone marrow to form haemoglobin. Biliverdin is formed from the protein part of the erythrocytes. It is then reduced to the yellow pigment bilirubin, before it is bound to plasma globulin and transported to the liver. In the liver it is changed from a fat-soluble to a water-soluble form before it is excreted as a constituent of bile. 221 Haemolysis Haemoglobin To release Heme Globin Biliverdin Iron Erythropoiesis Bilirubin Excreted in Bile 222 223 BLOOD GROUPS Antigens, found on the surfaces of individual’s RBCs, which are inherited, determine the individual's blood group. In addition, individuals make antibodies to these antigens, but not to their own type of antigen, since if they did the antigens and antibodies would react causing a transfusion reaction. These antibodies circulate in the bloodstream and the ability to make them is genetically determined and not associated with acquired immunity. 224 If individuals are transfused with blood of the same group, i.e. possessing the same antigens on the surface of the cells, their immune system will not recognise them as foreign and will not reject them. However, if they are given blood from an individual of a different blood type, i.e. with a different type of antigen on the red cells, their immune system will mount an attack upon them and destroy the transfused cells. This is the basis of the transfusion reaction; the two blood types, the donor and the recipient, are incompatible. There are two important systems of blood grouping: i. ABO system ii. Rhesus system 225 THE ABO SYSTEM About 55% of the population has either A-type antigens (blood group A), B-type antigens (blood group B) or both (blood group AB) on their red cell surface. The remaining 45% have neither A nor B type antigens (blood group O). The corresponding antibodies are called anti-A and anti- B. Blood group A individuals cannot make anti-A (and therefore do not have these antibodies in their plasma), since otherwise a reaction to their own cells would occur; they do, however, make anti-B. 226 Blood group B individuals, for the same reasons, make only anti-A. Blood group AB make nei

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