Dr Narmeen S. Ahmad
Tissues are groups of cells with a common structure (form) and function (job). There are (4) types of tissue: 1. Epithelial 2. Connective 3. Muscle 4. Nervous
Epithelial cells Epithelium is an avascular tissue. The locations of epithelial cells: Cover the exterior body surfaces line internal closed cavities (including the vascular system) Found in body tubes that communicate with the exterior (the alimentary, respiratory, and genitourinary tracts). Found in glands and their ducts.
Function of epithelial cells: Covering and protection Secretion and excretion Absorption Sensation
Feature of epithelial cells Packed and contiguous cells Little or no intercellular materials Cells are usually joined by a cell-to-cell junction. They are upon Basement membrane It separate epithelial cell and Connective tissue. It is non cellular membrane (proteinpolysaccharide rich membrane).
Feature of epithelial cells They have Microvilli Micorvilli are finger like cytoplasmic projections on the apical surface of most epithelial cells.
Feature of epithelial cells They bear Cilia on their free surface. Cilia are cytoplasmic and plasma membrane projection from apical surface Ciliated epithelial cells are found in respiratory system and fallopian tube. Cilia Epithelial cell
Feature of epithelial cells Some of epithelial cell covered by keratinized layers. Keratinization: The process in which the cytoplasm of the outermost cells of the mammalian epidermis is replaced by keratin. Keratinized layers protect underlying tissues.
Classification of Epithelial cells cells are classified into three main cell groups according to their shapes: 1. squamous (flat platelike) 2. cuboidal (height and width similar) 3. columnar (height 2 5 times greater than width)
Classification of Epithelial cells Depending on the layers, cell are classified into 1. One layer: simple epithelium 2. More than one layer: stratified epithelium Pseudostratified = false layered (appears to be more than one layer, but it is one layer). Pseudostratified
The tissue that forms a continuum with the other 3 major tissues to maintain a functionally integrated body. Functions of connective tissues: 1. Protection (eg: skull protects brain) 2. Connecting and binding (eg: tendons bind muscle to bone) 3. Storage (Eeg: bone stores calcium and phosphorous) 4. Transportation (eg: blood transports gases, nutrients and waste products) Connective tissues 5. Body defence (eg: macrophage in some tissue attack foreign particle) 6. Structural frame work (eg: skeleton in human body) 7. Cushion and insulation (eg: cartilage in joints)
Content of connective tissues 1. Cells 2. Protein fibres 3. Ground substance
Cells of connective tissues Fixed cells: cells differentiate from mesenchymal cells, such as adipocytes and fibroblasts; these cells are formed and reside in the connective tissue. Wandering cells: cells arise from hematopoietic stem cells, differentiate in the bone marrow and migrate from the blood circulation into connective tissue. such as: mast cells, macrophages, plasma cells, and leukocytes.
Connective tissue fibres 1. Collagenous fibers: composed of collagen 2. Reticular fibers: Very thin collagenous fibers 3. Elastic fibers: composed mainly of the protein elastin
Ground substance Colorless, transparent and homogenous Fills the space between cells and fibers of the CT. Formed mainly by two classes of components: I. Glycosaminoglycans II. Structural glycoproteins
Classification of connective tissues I. Connective Tissue Proper Loose connective Tissue (provides padding between and around organs and tissues) Dense connective tissue : Regular (found in tendons, and ligaments) Irregular (found in skin, and digestive tract) II. Specialized Connective Tissue Blood Adipose Reticular III. Supporting Connective Tissue Cartilage Hyaline (found in nose, trachea and ribs, limbs) Elastic (found in ear and epiglottis) Fibrocartilage (found in knee joint and intervertebral discs) Bone Compact bone Spongy bone
Proper connective tissue 1- Loose (Areolar) connective tissue Gel-like matrix with all three connective tissue fibers Cells: Fibroblasts, macrophages, mast cells, and some white blood cells Highly cellular, numerous cell types present. provides padding between and around organs and tissues.
2- Dense connective tissue A- Regular Dense CT: Parallel collagen fibers with a few elastic fibers Major cell type is fibroblasts Found in tendons, and ligaments
B- Irregular dense CT: Irregularly arranged collagen fibers with some elastic fibers Major cell type is fibroblasts Found in the dermis, submucosa of the digestive tract.
Supportive connective tissue a. Cartilage It is a type of connective tissue which is tough, and flexible. Unlike other CT, does not contain vessels and nerves. Most cartilage is surrounded by the perichondrium. Fibrocartilage is the exception.
1- Hyaline cartilage Amorphous, firm matrix with imperceptible network of collagen fibers Chondrocytes lie in lacunae
2- Elastic cartilage Similar to hyaline cartilage but with more elastic fibers Maintains shape and structure while allowing flexibility
3- Fibrocartilage Matrix similar to hyaline cartilage but less firm with thick collagen fibers Cells arranged singly or in long rows
Location of cartilages
b. Bone Bone is a hard and rigid tissue, consists of living cells with large amounts of matrix. Gross appearance: 1. Compact bone or cortical bone: 2. Spongy or cancellous bone:
Bone layers Periosteum.. The outer surface of bone is called the periosteum Compact Bone It provides most of the strength and support. Cancellous Bone (Spongy Bone) It is found within the compact bone as well as the end of long bones, it has many open spaces like a sponge. Bone marrow Red bone marrow Yellow bone marrow
Types of bone cells 1. Osteogenic cells: they are stem cells and differentiate to osteoblast. 2. Osteoblast cells: these are the bone cells that are responsible for bone formation. They function by secreting a substance called Osteoid, which is also known as the bone matrix. 3. Osteocyte: they are mature osteoclast that do not secrete the osteoid bone matrix. They play an important role in maintaining calcium levels in body fluids. 4. Osteoclast cells: these are the cells that are responsible for dissolving bone tissue.
Compact bone structure Compact bone consists of closely packed osteons or haversian systems. The osteon consists of a central canal called the osteonic (haversian) canal, which is surrounded by concentric rings (lamellae) of matrix. Between the rings of matrix, the bone cells (osteocytes) are located in spaces called lacunae.
Spongy bone structure Spongy (cancellous) bone is lighter and less dense than compact bone. Spongy bone consists of plates (trabeculae) and bars of bone adjacent to small, irregular cavities that contain red bone marrow. WHAT IS DIEFFERNCE BETWEEN COMACT AND SPONG BONE? Spongy bone tissue does not contain osteons. Instead, it consists of trabeculae, which are lamellae that are arranged as rods or plates.
Specialized connective tissues 1- adipose tissue Adipose tissue, or fat, is an anatomical term for loose connective tissue composed of adipocytes. Its main role is to store energy in the form of fat, although it also cushions and insulates the body.
2- Reticular connective tissue The reticular connective tissues are found in the kidney, the spleen, lymph nodes, and bone marrow. Their function is to form a stroma and provide structural support.
3- Blood It is a types of liquid connective tissue. Is a complex mixture of cells, chemicals and fluid. The main components of blood include is made up of plasma which is a highly viscous liquid and formed elements (white blood cells, red blood cells, and platelets).
Formed elements of blood a. Erythrocyte (RBC) RBCs constitute the largest number of cells in the blood RBCs are also known as erythrocytes (erythros = red). biconcave disc shape main function is gases transport due to the presence of haemoglobin.
b. Platelets (thrombocytes) Small, biconvex disks. Function: initiate blood clots
c. Leucocyte (WBC) main function is defence. classification of leukocytes classification system is based on appearance of the granule o Granulocytes Neutrophil, Basophile and Eosinophil o Agranulocytes Lymphocytes and Monocytes
Muscle tissue Functional classification is based on the type of neural control. Voluntary. Involuntary. Structural classification is based on the presence or absence of cross striations. Striated Non-striated (smooth) Combined functional and structural classification: Skeletal muscle Cardiac muscle Smooth (visceral) muscle
1. Skeletal muscle Each muscle is an organ Consists mostly of muscle tissue Connective tissue Blood vessels Nerves Skeletal muscles are: striated, voluntary, and multinucleated long, thin and cylindrical; they are attached to bones and move our skeleton. Muscle fiber nucleus (cell) Striations
Structural organization of skeletal muscle fiber Muscle fascicle: Collection of muscle fibers Muscle fiber: Skeletal muscle is made up of bundles of individual muscle fibers called myocytes. Each myocyte contains many myofibrils. Myofibrils: composed of bundles of overlapping myofilaments. Myofilaments: Visible only with the electron microscope; composed primarily of actin, and myosin Sarcomere: Contractile unit of striated muscle fibers, seen in both skeletal and cardiac muscle fibers. Extends from Z-line to Z-line. Sarcomeres are repeated in series along the length of each myofibril.
Structural organization of skeletal muscle fiber
2. Cardiac Muscles Cardiac muscle occurs only in the myocardium of the heart. Cardiac muscle tissue plays the most important role in the contraction of the atria and ventricles of the heart. Long cylindrical, involuntary, and usually one nucleus per fiber located in the center. Striated but more irregular due to branching of cells.
3.Smooth Muscles Smooth muscle occurs mostly as sheets, which form the walls of most hollow organs. Unbranched spindle-shaped fibers are elongated with pointed ends. Possess a single, centrally placed, oval nucleus and they are Non-striated
Nervous system The Nervous System is the master controlling system of the body. The nervous system is composed predominantly of neural tissue, but also includes blood vessels and connective tissue. Organization of the Nervous System The Central Nervous System (CNS) Consists of the brain and spinal cord with tracts and nuclei The Peripheral Nervous System (PNS) Consists of ganglia, cranial nerves, spinal nerves and peripheral receptors
Cells of Nervous Tissue Neurons Functional units of the nervous system; receive, process, store, and transmit information to and from other neurons, muscle cells, or glands. Neuroglia (supporting) cells Provide metabolic and structural support for neurons.
Structures of Neurons 1. Cell body: It consists of a nucleus with easily visible nucleolus and some special organelles Nissl bodies (rough ER) Neurofibrils (intermediate filaments to maintain cell structure). Well developed Golgi apparatus Numerous mitochondria
2. Dendrite(s) They are treelike extensions at the beginning of a neuron.
3. Axon An extension of the cell body that is specialized for conducting electrical impulses (action potentials).
4. Terminal Buttons and Synapses The terminal buttons are located at the end of the neuron and are responsible for sending the signal on to other neurons. At the end of the terminal button is a gap known as a synapse.