Tissues PDF - Gulf Medical University

Tissues Dr.Sapna S Assistant Professor of Anatomy www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES  Epithelial tissue: A sheet of cells which covers external surface or lines interior of the organs/ body cavities Classified bas...

Tissues Dr.Sapna S Assistant Professor of Anatomy www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES  Epithelial tissue: A sheet of cells which covers external surface or lines interior of the organs/ body cavities Classified based on shape and cell layers Shape squamous = thin, flat cells cuboidal = cube-shaped cells columnar = tall, elongated cells Number Simple = single layer Stratified = 2 or more layers Classes of Epithelia Based on shape and layers  Capillary endothelium Simple squamous epithelium Squama = scale like ✓Cells are flat and thin ✓Flattened nuclei ✓Helps in diffusion of gases and nutrients ✓E.g., endothelium, mesothelium, epithelium of the alveoli Alveoli Simple cuboidal epithelium ✓Height and breadth of the cell is equal ✓Nucleus is rounded Thyroid follicles ✓E.g., covering of ovary, lining of ducts, lining of thyroid follicle Ovary Renal ducts Simple columnar epithelium ✓Height of the cell more than its width ✓Elongated oval nuclei ✓Types Secretory simple Secretory goblet Absorptive with microvilli Ciliated Pseudostratified ciliated columnar epithelium ✓Single layer of cells appears to be 2 layered. ✓Cells are at different layers, only few reach the lumen. ✓Nuclei are also at different levels and hence looks stratified. ✓E.g., respiratory tract B. Stratified Epithelium 1. Stratified squamous epithelium keratinized & non keratinized. 2. Transitional epithelium 1. Stratified squamous epithelium – Multiple layers. – Basal cells are active & columnar in shape – The intermediate layers have polygonal cells. – Surface cells are flattened squamous.  – Found in places where there is wear and tear. Function: – Protection & prevents water loss. Non keratinized e.g. oral cavity, upper esophagus, conjunctiva, vagina. If keratinized, surface cells lose their nuclei ,cytoplasm replaced by keratin e.g. Skin 2. Transitional epithelium: – Consists of many cell layers. – Basal cells are low columnar – Several intermediate layers of polygonal cells – Surface layer of large rounded cells like umbrella. Site: Urinary tract (urothelium). Function: – Protection, capability of distention. – No secretion and No absorption. Empty bladder Distended(full) bladder CLASSIFICATION OF THE GLANDS BASED ON THE type a. Unicellular glands: Single secretory cell E.g., goblet cells (flask shaped) that are scattered all over the mucous membranes. b. Multicellular glands Group of epithelial cells The secretion is discharged either directly or through duct system. CLASSIFICATION OF MULTICELLULAR GLANDS: With ducts: exocrine glands Without ducts: endocrine glands Exocrine: pour their secretions onto an epithelial surface, directly or through ducts. Endocrine (ductless): pour their secretions directly into the blood. Classification of exocrine glands Based on shape of secretory unit & branching pattern of duct Based on mechanism of release of their product Based on the nature of their secretion  Mechanisms of gland secretion Apocrine Holocrine Merocrine The apical parts of the Release their products & Secrete their products epithelial cells are lost during the whole cell rupture. by exocytosis. the process of secretion. Salivary glands, sweat glands Sebaceous Glands Mammary glands BONE General features: Bone is one of the hardest substances in the body. It is a living tissue composed of cells , fibers and extracellular matrix. Hard, calcified matrix (mineralized) with collagen fibers are found in bone. The calcium salts are deposited in the ground substance. Osteocytes are found in lacunae and are well vascularized. Functions: Supports, protects, and provides levers for muscular action. Stores calcium, phosphorus minerals. Red Marrow inside bones is the site of hematopoiesis. Gross Anatomy of a long Bone Diaphysis Epiphysis Membranes Membranes Periosteum Endosteum Compact Bone Compact bone is arranged in units called osteons or Haversian systems. Osteon: Structural and functional unit of the Compact Bone The whole complex of concentric lamellae of the bone surrounding a canal containing blood vessels, nerves, and loose connective tissue is called a Haversian system, or osteon Osteocytes are found in spaces called lacunae Osteon Perforating (Volkmann’s) Canal Canals lie at right angles to long axis of bone Connect the vascular supply of the periosteum to those of the central canal and medullary cavity  Spongy Bone Spongy (cancellous) bone does not contain osteons. It consists of trabeculae surrounding many red marrow filled spaces. It forms most of the structure of short, flat, and irregular bones, and the epiphyses of long bones. Spongy bone tissue is light and supports and protects the red bone marrow. Found in ends of long bones and inside flat bones such as the hipbones, sternum, sides of skull, and ribs. Bone cell types 1. Osteoblasts: Immature bone cells. Located on the bone forming surfaces. They synthesize and secrete the osteoid matrix (uncalcified extracellular matrix). Matrix is composed of glycoproteins & collagen. They are not yet embedded in the osteoid matrix.  2. Osteocytes: Mature bone cells. Osteoblasts that have become embedded in calcified bone matrix. They reside in lacunae within the matrix. Are connected with neighboring osteocytes via cytoplasmic processes that extend through small tunnels called canaliculi. Lacunae are spaces around osteocytes 3. Osteoclasts: These are large multinucleated cells. Act to resorb bone during bone formation and healing, remodeling throughout life. Important in maintaining calcium balance in the body. Cartilage Modified connective tissue Forms skeletal basis of some parts of body Matrix is firm giving it the characteristic consistency Avascular (nutrients diffuse from the perichondrium) Covering of cartilage is Perichondrium : is rich in blood vessels CHONDROBLAST Progenitor of chondrocytes Lines border between perichondrium and matrix Secretes type II collagen and other ECM components  MATRIX Provides the rigidity, elasticity, & resilience FIBERS Collagen and elastic GROUND SUBSTANCE Glycosaminoglycans (chondroitin sulfates & keratan sulfate) Proteoglycans Water Basophilic TYPES OF CARTILAGE HYALINE ELASTIC FIBROUS  perichondrium HYALINE CARTILAGE cChondr  HYALINE CARTILAGE Sites: Tracheal rings, nasal septum, larynx, costal cartilage & articular surfaces of joints Cartilage cells: Present singly or in groups of 2 or 4 cells inside lacunae Cartilage Matrix: Collagen type II Ground substance: Homogenous, clearly basophilic Functions: supportive ELASTIC CARTILAGE  ELASTIC CARTILAGE Sites: Auricle, ext. auditory meatus, auditory tube, epiglottis, apices of arytenoid cartilage Cartilage cells: larger, more numerous, packed more closely Cartilage Matrix: elastic fibres, collagen type II Ground substance: Rich in elastic fibres Functions: supportive Fibrocartilage  FIBROCARTILAGE  Sites: intervertebral discs, pubic symphysis, manubriosternal joint, articular disc of TM joint.  Cartilage cells: fewer, smaller, scattered singly or in rows Cartilage Matrix: collagen type I & II Ground substance: acidophilic Functions: supportive with tensile strength Objectives: 1. Describe the different types of epithelial cells & the locations and the functions of each type.. 2. Describe the glandular tissue according to the shape of secretory unit, pattern of duct system, mechanism of secretion and the nature of the secretion 3. Differentiate the histology of bone 4. Describe the gross and microscopic structure of different types of cartilages Reference: Gartner, Leslie P.: Textbook of Histology, 5th Edition, 2021 Elsevier. IBSN 978-0-323-67272-6. Chapter (5) Types of epithelium https://www-clinicalkey-com.gmulibrary.com/#!/content/book/3-s2.0- B9780323672726000059 Glandular epithelium https://www-clinicalkey-com.gmulibrary.com/#!/content/book/3-s2.0- B9780323672726000059?scrollTo=%23hl0001194 Textbook of Histology,5th edition-2021,Leslie P. Gartner,Chapter 6,Page 103-124,ISBN 978-0-323-67272-6 https://www-clinicalkey-com.gmulibrary.com/#!/content/book/3-s2.0- B9780323672726000060 35