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Transcript
Cells and tissues Published by Hodder Education © 2010 Helen McGuinness 1 Objectives By the end of this chapter you will be able to recall and understand the following knowledge: the different levels of structural organisation in the body the importance of homeostasis and metabolism in correct body functioning parts of a cell’s structure and their functional significance Published by Hodder Education © 2010 Helen McGuinness 2 Objectives the structure and function of the main tissue types in the body the interrelationships between the cells and tissues and other body systems common pathologies associated with cells and tissues. Published by Hodder Education © 2010 Helen McGuinness 3 Key words atom molecule cell tissue organ system homeostasis metabolism cell membrane cytoplasm nucleus nucleolus nuclear membrane lysosome vacuole ribosome Golgi body mitochondria centrosome centromere centrioles chromatid diffusion osmosis active transport filtration cell respiration tissue fluid meiosis mitosis Published by Hodder Education © 2010 Helen McGuinness 4 Structural organisation of the body The human body involves five levels of structural organisation – atoms and molecules, cells, tissues, organs and systems. Atoms and molecules are the lowest level of organisational complexity in the body. Cells are the smallest units that show characteristics of life. Published by Hodder Education © 2010 Helen McGuinness 5 Structural organisation of the body Tissues are a group of similar cells that perform a certain function. Organs are tissues grouped into structurally and functionally integrated units. Systems are a group of organs that work together to perform specific functions. Published by Hodder Education © 2010 Helen McGuinness 6 Structure of a cell A cell is the basic, living, structural and functional unit of the body. The principal parts of the cell are the cell membrane and its organelles which play specific roles in cellular growth, maintenance, repair and control. The cell membrane encloses the cell and protects its contents. It is semi-permeable and governs the exchange of nutrients and waste materials. The nucleus controls the cell’s activities and contains the genetic information. Published by Hodder Education © 2010 Helen McGuinness 7 Structure of a cell The cytoplasm is the substance inside the cell between the plasma membrane and the nucleus. The ribosomes are sites of protein synthesis. The endoplasmic reticulum links the cell membrane with the nuclear membrane and assists movement of materials out of the cell. Published by Hodder Education © 2010 Helen McGuinness 8 Structure of a cell The Golgi body processes, sorts and delivers proteins and lipids (fats) to the plasma membrane, lysosome and secretory vesicles. The lysosome is a round sac in the cytoplasm that contains powerful enzymes to help destroy waste and worn out cell materials. The mitochondria are the ‘powerhouses’ of the cell. Published by Hodder Education © 2010 Helen McGuinness 9 Structure of a cell The centrosome is a dense area of cytoplasm, containing the centrioles. The centrioles are paired small spherical structures associated with cell division, or mitosis. The chromatids are a pair of identical strands that are joined at the centromere and separate during cell division. The centromere is the portion of a chromosome where the two chromatids are joined. Published by Hodder Education © 2010 Helen McGuinness 10 Structure of a cell Published by Hodder Education © 2010 Helen McGuinness 11 Functions of cells Functions of cells include respiration, growth, excretion, movement, irritability and reproduction. Published by Hodder Education © 2010 Helen McGuinness 12 Cellular respiration Cells function through the exchange of fluids, nutrients, chemicals and ions which are carried out by passive processes such as diffusion, osmosis and filtration, and active processes such as active transport. Cell respiration is the controlled exchange of nutrients such as oxygen and glucose and waste such as carbon dioxide by the cell to activate the energy needed for the cell to function. Published by Hodder Education © 2010 Helen McGuinness 13 Cellular respiration The fuel required by cells is provided by glucose from carbohydrate metabolism and oxygen absorbed from the respiratory system into the bloodstream. Cells are bathed in a fluid known as tissue fluid or interstitial fluid which allows the interchange of substances between the cells and the blood, known as internal respiration. Published by Hodder Education © 2010 Helen McGuinness 14 The cell’s life cycle Cell division is the process by which cells reproduce themselves. Mitosis is cell division that results in an increase in body cells and involves division of a nucleus. Meiosis is reproductive cell division and results in the fusion of an egg and a sperm into a zygote. Published by Hodder Education © 2010 Helen McGuinness 15 Introduction to tissues A tissue is a group of similar cells that are specialised for a particular function. The tissues of the body are classified into four main types: epithelial, connective, muscular and nervous. Published by Hodder Education © 2010 Helen McGuinness 16 Epithelial tissue Epithelial tissue provides coverings and linings of many organs and vessels. There are two categories of epithelial tissue: simple (single layer) and compound (multi-layer). There are four different types of simple epithelium: squamous, cuboidal, columnar and ciliated. There are two different types of compound epithelium: stratified and transitional. Published by Hodder Education © 2010 Helen McGuinness 17 Epithelial tissue Type Simple squamous Structure Location Function A single layer of flat, scale-like cells with a central nucleus The cells fit closely together, rather like a pavement, producing a very smooth surface Lines the alveoli of the lungs Simple cuboidal Single layer of cube-like cells Ovaries, kidney tubules, thyroid gland, pancreas and salivary glands Secretion and absorption Simple columnar Single layer of tall, cylindrical column cells with nucleus situated towards base of cell Lines the small and large intestine, stomach and gall bladder Secretion and absorption Lines blood and lymphatic vessels and the heart Allows for exchange of nutrients, wastes and gases Published by Hodder Education © 2010 Helen McGuinness 18 Epithelial tissue Type Simple ciliated (columnar) Structure A form of columnar epithelium Single layer of rectangular cells that contain hair-like projections (cilia) from its surface Location Function Lines the upper part of respiratory system Also lines the uterine tubes The beating of the cilia carries unwanted particles along with mucus out of the system Helps propel the ova towards the uterus Published by Hodder Education © 2010 Helen McGuinness 19 Connective tissue Connective tissue is the most abundant type of body tissue. It connects tissues and organs to give protection and support. Connective tissue consists of the following different types: areolar, adipose, white fibrous, yellow elastic, lymphoid, blood, bone and cartilage. Published by Hodder Education © 2010 Helen McGuinness 20 Connective tissue Type Structure Location Function Areolar Most widely distributed type of connective tissue in body A loose, soft and pliable tissue containing collagen, elastin and reticular fibres Under the skin, between muscles, supporting blood vessels and nerves and in the alimentary canal Provides strength, elasticity, connects and supports organs Adipose A type of areolar tissue containing fat cells (adipocytes) Surrounds organs such as kidneys and heart Under the skin (subcutaneous layer) between bundles of muscle fibres, in yellow bone marrow of long bones and as a padding around joints Provides insulation, support and protection Emergency energy reserve Published by Hodder Education © 2010 Helen McGuinness 21 Connective tissue Type Structure Location Function White fibrous Strong, connecting tissue made up of mainly closely packed bundles of white, collagenous fibres, with very little matrix Contains cells called fibrocytes between bundles Forms tendons which attach muscle to bone, ligaments which tie bones together and as an outer protective covering for some organs such as the kidney and bladder Provides strong attachment between different structures Yellow elastic Consists of branching yellow elastic fibres with fibrocytes in the spaces between the fibres Arteries, trachea, bronchi and lungs To allow stretching of various organs, followed by a return to original shape and size Lymphoid Semi-solid matrix with fine branching fibres Specialised cells called lymphocytes In the lymph nodes, spleen, tonsils, adenoids, walls of the large intestine and glands in small intestine Forms part of the lymphatic system whose function is to protect the body from infection Published by Hodder Education © 2010 Helen McGuinness 22 Connective tissue Type Structure Location Function Blood Also known as liquid connective tissue, contains the blood cells erythrocytes, leucocytes and thrombocytes which float within fluid called plasma Contained within blood vessels Helps maintain homeostasis of the body by transporting substances throughout the body, by resisting infection and maintaining heat Bone Hardest and most solid of all connective tissues Tough, dense compact bones and slightly less dense cancellous bone Bones Protects and supports other organs and soft tissues Cartilage Much firmer tissue than other connective tissues; matrix is quite solid See next slide on types of cartilage See next slide on types of cartilage Published by Hodder Education © 2010 Helen McGuinness 23 Cartilage Type Description Location Function Hyaline cartilage Most abundant cartilage found in the body Smooth, bluish-white, glossy tissue Contains numerous cells called chondrocytes from which cartilage is produced Found on the surfaces of the parts of bones which form joints Forms costal cartilage which attach ribs to sternum Forms part of the larynx, trachea and bronchi Provides a hardwearing low friction surface within joints Provides flexibility in the nose and trachea White fibrous cartilage Tough but slightly flexible Composed of bundles of collagenous white fibres in a solid matrix with cells scattered among them As pads between the vertebrae called the intervertebral discs and in the symphysis pubis which joins pubis bones together Support and to join together or fuse certain bones Yellow elastic fibrocartilage Yellow elastic fibres running through solid matrix, between which chondrocytes are situated Forming the pinna (lobe of the ear) and forming the epiglottis Provides support and maintains shape Published by Hodder Education © 2010 Helen McGuinness 24 Membrane Type Description Location Function Mucous membrane Lines body cavities and outer layer of organs Lines respiratory, digestive, urinary and reproductive tracts Lines openings to external environment and secretes viscous slippery fluid (mucus) that coats and protects underlying cells Serous membrane Lines body cavities not open to external environment and covers many organs Two layers: parietal which lines the wall of body cavities and visceral which provides external covering to organs in body cavities Pericardium of the heart Pleural membranes in the lungs Peritoneum lining the abdominal organs Lines body cavities not open to external environment and secretes a thin, watery (serous) fluid that lubricates organs to reduce friction as they rub against one another and against wall of cavities Synovial membrane Lines joint cavities of freely movable joints Lines spaces around certain joint cavities (shoulder, hip and knee) Secretes synovial fluid that provides nutrition and lubrication to joints so they move without undue friction Published by Hodder Education © 2010 Helen McGuinness