Histology is the study of tissues A TISSUE is a group of cells, usually of one kind, & their intercellular substance (e.g. intercellular matrix in animal) which are linked together & perform a particular function Tissues organs system organism pg151
The classification of animal tissues
Epithelial tissues Arranged in single or multilayered sheets Cells tightly junked together Covered the internal and external surfaces of the body Lines, covers, and protects other tissues and organs. Lack blood vessels -epithelium shows a very rapid rate of cell division so that lost cells are replaced speedily. pg152
*Have one free surface *Bottom layer of cells rest on a basement membrane consisting of a network of collagenous fibres pg152
Epithelial tissues Functions: - protect underlying structures from injury through pressure and from infection. -secretion -absorption -sensation -reproductive Pg 152
**True epithelium is classified into simple (one cell thick) and compound (more than one cell thick) epithelium Named by Cell shape Squamous, Cuboidal,andColumnar pg153
Squamous Epithelium Cells very thin, much wider than they are thick. Thin, flattened and contain little cytoplasm. The margins of the cells are irregular (tessellated) Simple Squamous Epithelium Air sacs of respiratory Lining of blood vessels, heart and lymphatic tubes Stratified Squamous Epithelium Skin Esophagus Mouth Pg 154
Examples of Simple Squamous Epithelium Jenna Hellack Jan 2001
Simple Cuboidal Epithelium Cells cube shapedfunctions -secretion and absorption. site -Kidney tubules -Duct and small glands -Surface of ovary pg154 Jenna Hellack Jan 2001
Simple Cuboidal Epithelium
Connective Tissue _Characterized by the cells widely separated from each other in a matrix that is produced by the cells. -Tissue protects and supports. -Cell Matrix composed of two regions 1-Ground Liquid (sol), Gel, Gum or solid 2-Fibers Non-elastic (= white or Collagen) Elastic (= yellow fibers) Pg 157 Jenna Hellack Jan 2001
Types of Connective Tissue Loose (Areolar) Connective Tissue Dense Connective Tissue Adipose Cartilage Bone Blood Jenna Hellack Jan 2001
Connective tissues 1-Loose connective tissue - Areolar tissue contains a mixture of mucin, hyaluronic acid. Scattered throughout are numerous wavy bundles of collagen fibres and elastin Gel like ground -interspersed in the matrix are a variety of different cell types: fibroblasts, macrophages, reticuloendothelial system and mast cells site Wraps and cushions organs Under the skin pg158
Loose Connective Tissue (Areolar) Jenna Hellack Jan 2001
Dense Regular Connective Tissue -. tough, shiny tissue with highly organized bundles of collagen fibres closely packed and running parallel. -. rows of fibroblasts are interspersed among the collagen and run alongside the bundles. -. each bundle is bound to its neighbours by areolar tissue. -. tissue is strong, flexible, inextensible and dense. -. present in tendons, ligaments, cornea of the eye, kidney capsule. Pg 158.159 Jenna Hellack Jan 2001
Dense Regular Connective Tissue
Adipose (Fat) Found in dermis of the skin, mesenteries and around the kidneys and heart Functions: Tissue provides energy reserve, acts as a shock absorber and insulates against heat loss. storage cells for adipose Jenna Hellack Jan 2001
Adipose tissue has no specific matrix and contains large number of fat cells arranged into lobules. each cell is filled almost entirely by a central fat droplet which squeezes the cytoplasm and nucleus to the periphery. Adipose cells contain a large vacuole which in the live cell contains lipids.
Adipose tissue
Vascular Tissue (Blood) Blood is a connective tissue of cells separated by a liquid (plasma ) matrix. Two types of cells occur. Red blood cells (erythrocytes) carry oxygen. White blood cells (leukocytes) function in the immune system. Plasma transports dissolved glucose, wastes, carbon dioxide and hormones, as well as regulating the water balance for the blood cells. Platelets are cell fragments that function in blood clotting. Pg 159-160 Jenna Hellack Jan 2001
Blood Jenna Hellack Jan 2001
Cartilage Ground of matrix is gum like. Cells are found in Lacunae within the matrix. Fibers may be elastic or non-elastic, or a form of nonelastic called reticular(where the non-elastic fibers of very thin) Types of cartilages: Hyaline cartilage: occurs in larynx, trachea and bones of embryo. pg161 Jenna Hellack Jan 2001
Constists of cells embedded in a matrix of chondrin which is deposited by chondroblasts The matrix consists of many fibrils and collagen The space called lacunae encloses chondroblasts Cartilage is hard but flexible tissue and can resist any strains. The matrix is also compressible and elastic. pg161
Hyaline cartilage Jenna Hellack Jan 2001
Compact bone Ground of matrix is Solid (Calcium carbonate). Organic matrix The matrix of compact bone consists of bone collagen, hydroxyapatite, magnesium carbonates, sodium carbonates and nitrates.with small amount of white fibre. Pg 162,163 Has blood supply and nerves running through the Haversian canal systems. Jenna Hellack Jan 2001
A cross section of compact bone consists of cylinders of concentric bony lamellae which surrounds the central Haversian canal.
Interspersed between the lamellae are numerous lacunae containing bone cells called osteoblasts which are then termed as osteocytes when they are not active. Radiating from each lacunae are many fine channels called canaliculi which contain cytoplasm and link the central Haversian canal. pg163
Transverse section of a long bone Haversian canal canaliculi lacuna containing osteocyte lamellae
Cross section of compact bone
Muscle Tissue Tissue with cells having fibers specialized for contraction. Skeletal Muscle (Striated, voluntary) Parallel elongated cells (fibers) are subdivided into sarcomeres. multinucleated and each cell is the length of the muscle Svariable positions near the periphery of fibre. Attached to the skeleton in the trunk, limbs and head. Pg163-164 Jenna Hellack Jan 2001
Skeletal Muscle L.s Cs
Diagram of the arrangement of muscle fibrils
Nerve cell is called neurone. The main function is the conduction of impulses. Each neurone consists of a cell body with a nucleus, cytoplasm. The cytoplasmic processes extending from the cell body are dendrons (carry impulses towards the cell body) and axons (carry impulses away from the cell body). Pg165-166 Nervous tissue
Diagram of two neurones