Animal Histology PDF

Biolog110 ANIMAL HISTOLOGY THE EPITHELIAL TISSUES  GENERAL CHARACTERISTICS 1. Derived from 3 germ layers 2. Densely-packed cells 3. Little or no intercellular material in between cells 4. Cells with prominent nucleus. 5. Rests on a basement membrane 6. Cells are active in mito...

Biolog110 ANIMAL HISTOLOGY THE EPITHELIAL TISSUES  GENERAL CHARACTERISTICS 1. Derived from 3 germ layers 2. Densely-packed cells 3. Little or no intercellular material in between cells 4. Cells with prominent nucleus. 5. Rests on a basement membrane 6. Cells are active in mitosis – high regeneration. 7. Avascular – nourished by underlying CT 8. Polarity and cell surface modifications CLASSIFICATION  CLASSIFICATION A. SIMPLE EPITHELIA (one layer of cells) 1. Simple Squamous – flat, thin, and scale-like with central spherical nucleus. Polygonal in surface view. Endothelium – lining of blood vessels Mesothelium – lining of body cavities; pleura, pericardium,peritoneum, Bowman’s capsule. 2. Simple Cuboidal – rectangular, central spherical nucleus. eg. kidney, ovary, thyroid, small ducts. 3. Simple Columnar – pillar-like, basal oval nucleus e.g. GI tract, large ducts, uterus, oviduct Simple Epithelia  Simple Cuboidal Simple Columnar Simple Squamous CLASSIFICATION B. STRATIFIED EPITHELIA (2 or more layers of cells, consist of superficial, intermediate, and basal layers. 1. Stratified Squamous – keratinized – no nuclei on the uppermost layer. Found in the epidermis of the skin (“dry epithelium”) non-keratinized – nuclei present on the uppermost layer. e.g. oral cavity, esophagus, vagina, anal canal (“wet epithelia”)  CLASSIFICATION 2. Stratified Cuboidal – two layers of cuboidal cells, rare type. Ducts of sweat gland and salivary gland. 3. Stratified Columnar – large ducts, male urethra, conjunctiva 4. Transitional – appearance varies according to functional state of the organ. e.g. ureter and urinary bladder. - distended (2-4 with flattened superficial cells) - contracted (4-6 with dome-shaped superficial cells. 5. Pseudostratified - seemingly multi-layered due to unequal sizes of cells and nuclei at different levels; but all cells rest on a basement membrane. - ciliated ( e.g. trachea and respiratory tract) - stereociliated ( e.g. epididymis) POLARITY & SPECIALIZATION OF EPITHELIAL TISSUE A. APICAL/DISTAL – facing the lumen/free surface. 1. Cilia – beat in waves to move mucus and trapped materials; respiratory tracts (PCCE) and oviducts (SCCE). 2. Flagella – also for movement; one or two per cell; sperm motility. CILIA STRUCTURE (EM) A. APICAL/DISTAL 3. Microvilli – a. PM–covered extensions of the cell surface; cores with numerous parallel actin microfilaments b. resolvable only at EM. c. inc. surface area for absorption  4. Basal body – thin dense line at the base of cilia e.g. trachea. 5. Stereocilia – long, thin cluster of microvilli seen as wavy tapering projections. e.g. epididymis and ductus deferens (absorptive) ; hair cells of the organ of Corti (sensory function) GLANDS A. GLAND DEVELOPMENT EXOCRINE – duct-gland - Water containing enzymes via duct system to surface ENDOCRINE – duct-less gland - Hormones through capillary networks to the target cells or organs  GLANDS B. CLASSIFICATION OF EXOCRINE GLANDS 1. Number of cells a. Unicellular – e.g. goblet cells b. Multicellular - e.g. salivary gland 2. Arrangement of duct a. Simple – unbranched to one generation b. Compound – branched 3. Shape of secretory unit a. Tubular b. Saccular/alveolar PRINCIPAL TYPES OF EXOCRINE GLANDS SPECIFIC TYPES BASED ON ARRANGEMENT OF DUCTS AND SHAPE OF SECRETORY UNITS 1. SIMPLE – unbranched duct a. Tubular – straight, U-shaped intestine b. Coiled tubular – sweat gland c. Alveolar – sac/flask-like – poison gland d. Branched alveolar/acinar – sebaceous gland e. Branched tubular – GIT glands, uterus 2. COMPOUND – branched duct a. Tubular – cardiac gl, oral cavity b. Tubulo-acinar – submandibular, mammary c. Alveolar – exocrine pancreas IV. GLANDS B. CLASSIFICATION OF EXOCRINE GLANDS 4. Nature of secretory products a. Serous gland – water (often containing enzymes) e.g. parotid gland) b. Mucus gland – mucus (viscous glycoprotein) e.g. goblet c. Mixed gland – submaxillary gland 5. Mode of Secretion a. Merocrine – no loss of cytoplasm. exocytosis. e.g. b. Apocrine – loss of apical cytoplasm + secretory product e.g. ? c. Holocrine – entire cell released together with the secretion. e.g.? EPITHELIUM TYPES BASED ON FUNCTION  Membrane Epithelium  Glandular Epitheliun  Myoepithelium  Neuroepithelium  MYOEPITHELIAL CELLS (BASKET CELLS) Present in some exocrine glands - Located between secretory epithelial cells and basal lamina - Contain microfilaments and are contractile - Help eject secretion from gland NEUROEPITHELIUM Specialized Epithelia: -Olfactory epithelium -3 Types of cells: -Olfactory cells -Sustentacular cells -Basal cells THE CONNECTIVE TISSUES Connective Tissue  Characteristics  Basic Components  cells  extracellular matrix  fibers  ground substance  CLASSIFICATION OF CONNECTIVE TISSUES I. CT PROPER II. SPECIALIZED CT A. Loose CT A. Cartilage B. Dense CT 1. Hyaline 1. Dense Ireegular 2. Elastic 2. Dense Regular 3. Fibrocartilage C. Modified “Loose” B. Bone 1. Adipose Tissue 1. Compact 2. Reticular Tissue 2. Spongy 3. Mucous CT C. Blood 4. Elastic CT 1. WBC 5. Pigment Tissue 2. RBC 6. Lamina Propria 3. Platelet A. CONNECTIVE TISSUE PROPER - predominance of fibers - subtypes based on type, density, and orientation of its fibers. 1. Loose Connective Tissue (areolar tissue) - very disorganized - cells >> fibers (loosely arranged) - moderately viscous cytoplasm  CONNECTIVE TISSUE PROPER Cell components: fibroblasts, fibrocytes, mast cells, macrophage, adipocytes ,plasma cells, mesenchymal cells) Fiber components: collagen fiber, elastic fiber, reticular fibers Ground substance: proteoglycans, glycosaminoglycans FEATURES COLLAGEN FIBER ELASTIC FIBER RETICULAR FIBER Abundance Most Less Least Thickness 1-15 μm 0.1-10 μm 0.1-1.5 μm LM Appearance Straight, faintly Branched; net-like; Delicate network; silver eosinophilic, impregnation; argyrophilic Mechanical Property Tensile strength: tough Pliable and elastic Pliable Molecular Structure Procollagen; Elastin Type III collagen tropocollagen Location Type I –tendon dermis Hemopoietic organs, Type II –cartilage etc sinusoids, liver, dermis Loose Connective Tissue Location and Functions: - Underlies and supports most epithelia - Fills spaces between other tissues - Supports the serous membranes of (mesothelia) of the pleura, pericardium, and peritoneum. - Since well-vascularized : conveys oxygen and nutrients to avascular epithelia.  2.0 Dense Connective Tissue Dense Irregular CT - collagen bundles in a woven pattern that provides resistance to tensile stress from any direction. - LOCATION: reticular layer of the dermis Dense Regular CT - collagen fibers densely packed into parallel bundles - little room for ground substance - great tensile strength - LOCATION: found in tendons, ligaments, periosteum, perichondrium, deep fascia, and some organ capsules. 3.0 Modified “Loose”  Adipose Tissue  Reticular Tissue (reticular fibers=Type III collagen; very little ground substance; functions in support of motile cells; hematopoietic tissues)  Elastic CT (elastic fibers dominant; provides flexible support; limited to ligamenta flava of the VC, and suspensory ligament of the penis)  Mucous Connective Tissue (small number of cells and fibers in an abundant ground substance; jelly-like consistency; composed chiefly of hyaluronic acid; predominant component of the Wharton’s jelly of the umbilical cord, nucleus pulposus, and pulp of young teeth.  Pigment Tissue  Lamina Propria 3.1. Specialized Connective Tissue (matrix is either liquid, semisolid, or hard solid) A. CARTILAGE (semisolid gel) Cell component: chondrocytes Ground substance: chondroitin-sulfate and hyaluronic acid Fibers: collagen fiber, elastic fiber, reticular fiber Types: hyaline cartilage (nose, trachea, larynx) elastic cartilage (external ears, epiglottis) fibrocartilage (intervertebral disk, pubic symphysis) Terms: perichondrium, appositional and interstitial growth  Mitosis → cellular Chondroblasts Chondrocytes Mesenchyme tissue D.Hyaline GROWTH Cartilage - newly-formed chondrocytes deposit matrix around themselves; enhanced by GH, thyroxine, and testosterone; inhibited by estradiol and excess cortisone. 1. INTERSTITIAL GROWTH - division of existing chondrocytes giving rise to isogenous groups 2. APPOSITIONAL GROWTH - differentiation into chondrocytes by chondroblasts and stem cells on the inner surface of the perichondrium; responsible for girth increase of cartilage mass. BONE (hard mineral matrix)  Cell component: osteoblasts, osteocytes, osteoclasts  Osteoblast – bone deposition (active)  Osteoblast – mature bone cells  Osteoclast – bone resorption  Ground substance: calcium phosphate, chondroitin- sulfate, keratin sulfate  Fibers: “masked” collagen  GENERAL FEATURES OF BONE  Main constituent of the ADULT skeletal system (supportive and protective function) A. COMPOSITION 1. Bone cells (osteocytes, osteoblasts, and osteoclasts) o Osteoclasts: These are large, multinucleated cells responsible for bone resorption. o Osteoblasts: These are bone-forming cells that synthesize bone matrix. They produce collagen and other organic components of the extracellular matrix, which later mineralize to form bone o Osteocytes: These are mature bone cells embedded in the bone matrix. They are derived from osteoblasts and function to maintain bone tissue by regulating mineral content and responding to mechanical stresses. 2. Fibers (Type 1 collagen) 3. Ground Substance (inorganic salts) B. FUNCTIONS 1. Supports and protects the more fragile tissues and organs 2. Harbors the hematopoietic tissue (bone marrow) 3. Acts as leverage for muscle movement 4. Storage site for calcium and other minerals LACUNA OSTEOCYTES CANALICULI -Slender branching tunnels (0.1-0.2 um) radiating from lacuna of osteocytes -Where the nutrients derived from blood vessels flow THE BLOOD (liquid matrix)  Cell component: erythrocytes, leukocytes, thrombocytes  Ground substance: liquid plasma  Fibers: fibrin (collagen)  Terms: erythrocytes, monocytes, lymphocytes, B-cells,T-cells, neutrophils, eosinophils, basophils, thromobocytes, megakaryocytes  Functions of the Blood Tissue  Transporting oxygen from the lungs to tissues and carbon dioxide from tissues to the lungs.  Delivering nutrients like glucose, amino acids, and lipids to cells for energy and growth.  Removing waste products such as urea and creatinine from cells to be excreted by the kidneys.  Regulating body temperature by distributing heat throughout the body.  Maintaining pH balance by buffering acids and bases to keep the body’s environment stable.  Fighting infections through white blood cells that combat pathogens.  Clotting to prevent excessive blood loss after injury by forming blood clots.  Transporting hormones to help regulate various physiological processes. EOSINOPHILS  EM of a monocyte MONOCYTE – with a kidney-shaped Golgi nucleus with delicately-stained chromatin Mitochondria CYTOPLASM – slightly basophilic Azurophilic granules rER poorly-developed A BASOPHIL WITH MANY GRANULES COVERING THE CELL NUCLEUS EM OF A RABBIT BASOPHIL LOBULATED NUCLEUS APPEARS AS 3 SEPARATED PORTIONS NOTE THE BASOPHILIC GRANULE (B), MITOCHONDRIA (M), AND GOLGI COMPLEX (G) THE MUSCULAR TISSUES I. GENERAL FEATURES  Composed of differentiated cells containing contractile proteins (actin and myosin)  Actin (thin myofilaments)  Myosin (thick myofilaments)  Mesenchymal cell → lengthening + synthesis of myofibrillar proteins → muscle cells  A muscle cell = muscle fiber (myofiber)  THREE TYPES OF MUSCLE TISSUE  SKELETAL MUSCLE  Attached to skeleton  Bundles of long, cylindrical, multinucleated cells showing cross striations  Contraction is quick, forceful, voluntary control  CARDIAC MUSCLE  Associated with heart and roots of large bv  Elongated, branched individual cells separated by intercalated disks  Contraction is involuntary, vigorous, and rhythmic.  SMOOTH MUSCLE  Visceral muscle  Fusiform cells showing no striations under LM.  Contraction weak, slow, and not subject to voluntary control  TERMINOLOGY  Prefix “sarco”  Sarcolemma (plasma membrane)  Sarcoplasm (cytoplasm)  Sarcoplasmic reticulum (sER)  Prefix “myo”  myoglobin (hemoglobin) COLLAGEN I AND III  G Nuclei seen at the periphery, just under theA cell membrane G A G Myotendinous region: The insertion of collagen fibers of the tendon into the complex infoldings of the sarcolemma A BAND I BAND Z-LINE Section of heart muscle, showing central nuclei, cross striation, and intercalated disks THE NERVOUS TISSUES NERVOUS TISSUE  NERVE CELLS (neurons)  NEUROGLIAL CELLS (glial cells) THE SUPPORTING CELLS  Also called neuroglia “nerve glue”  Vary greatly accdg to their functions  Structural and nutritional support of neurons  Electrical insulation  Enhancement of the speed of impulse conduction along axons NOTE: It is difficult to maintain neurons in tissue culture without supporting cells. THE NEURONS  Performs all specialized functions attributed to nerve tissue  Receive and integrate stimuli from many sources simultaneously  Translate stimuli into action potentials  Propagate this electrical message rapidly over long distances and along specific pathways.  Transform the electrical message into specific neurotransmitters  Delivers the message to the target cells  PARTS OF A NEURON  CELL BODY  Nucleus  Cytoplasm  NERVE PROCESSES  Axons  Dendrites  TERMINAL BOUTONS A Typical Multipolar Neuron Ultrastructure of a Neuron