University:
Texas A&M University
Course:
BIOL 319 | Integrated Human Anatomy and Physiology I
Academic year:

2020
Views:

213

Pages:

65
Author:

Nossardisd7p

Epithelium (One of four basic types of Tissue) Objectives Embryonic origin and tissue organization Cell junction and cell polarity How to classify epithelia? Different types of glands and mechanisms of glandular secretion Four basic types of tissues in the body Epithelium (90% of tumors) Muscular tissue Connective tissue Nervous tissue Protoplasm – Living Substance CELL – Smallest unit of protoplasm Simplest animals consist of a single cell. CELL TISSUE – Groups of cells with same general function and texture (texture = tissue) e.g., muscle, nerve, connective tissue, epithelium TISSUE ORGAN ORGAN – Two or more types of tissues; larger functional unit e.g., skin, kidney, intestine, blood vessels ORGAN SYSTEM - Several organs e.g., respiratory, digestive, reproductive systems SYSTEM Epithelium Functions: cover organs, line viscera and blood vessels, and secretory cells of glands Distinguishing features and distribution: Always sit on a basement membrane, but come in a variety of configurations: classified on the basis of the shape of the surface cells and whether one (simple) or more (stratified) layers of cells are stacked upon each other. These cells are always attached to their neighbors by desmosomes, tight junctions, and gap junctions. Epithelia: Histological Identification Simple squamous – single layers of flat cells (blood vessels, covering of organs) Simple cuboidal – single layer of square cells (kidney tubules, liver cells, many others) Simple columnar – single layer of tall, thin cells (intestinal epithelium) Stratified squamous – multiple layers of cells with flat ones at the surface (skin, gums) Epithelia Pseudostratified columnar – single layer of tall, thin cells packed together in such a jumble that they seem to be in layers, although all of the cells reach the basement membrane (respiratory passage) Transitional – stratified cuboidal epithelium of urinary passage Some epithelia have surface specializations such as numerous microvilli or cilia. Others have enfolded base. Intestines Kidney distal tubule Origin and Distribution of Epithelium Ectoderm - epidermis of skin and epithelium of cornea together covers the entire surface of the body and oral cavity; sebaceous and mammary glands: anterior pituitary ECTODERM Endoderm - alimentary tract, liver, pancreas, gastric glands, intestinal glands • Endocrine glands - lose connection with surface Mesoderm Endothelium - lining of blood vessels Mesothelium - lining serous cavities MESODERM ENDODERM Epithelia are Specialized for Functions Absorption - intestine Secretion – pancreas Transport - eye, endothelium in vessels Excretion – kidney Protection – against mechanical damage and dehydration Sensory reception –pain to avoid injury, taste buds, olfactory, etc. Contraction – myoepithelium Intercellular canaliculus Salivary gland Mammary gland Sensory cells are of epithelia Surface Specializations of Epithelia 1. 2. 3. 4. Microvilli - intestine absorptive cell Cilia - respiratory epithelium Basal lamina - all epithelium Intercellular canaliculus hepatocyte 5. Secretory (intracellular) canaliculus - gastric parietal cell 6. Flagella Surface specializations of epithelia Surface specializations of epithelia Secretory (intracellular) canaliculus – gastric parietal cell Surface specializations of epithelia 155 Bile (intercellular) canaliculus –hepatocyte Surface specializations of epithelia Intercellular canaliculus –salivary gland Surface specializations of epithelia flat cells for easy passage of blood fluid and cells Endothelium - active cell Has enzymes and receptors Transport without much energy Flat for less turbulence Negatively charged surface Not wettable surface UT 196 Surface specializations of epithelia Milk Tears Bile Transcytosis Cervical fluid to get antibodies into secretions Etc. Specialization of Epithelia Maintain extensive contacts among cells (little space between cells). Structurally and functionally polarized. Junctions Zonula occludens – tight junction (belt) Zonula adherens – adhering belt Desmosome (macula adherens) - spot attachment Gap junctions - communication Terminal bars Terminal bars Belts around each cell Zonula Occludens - Tight Junction (Belt) Zonula Occludens – Tight Junction (Belt) It establish regional membrane fluidity of membrane proteins = Keeps symports and uniports seperate Zonula Occludens - tight junction (belt) Zonula Occludens - tight junction (belt) Zonula Adherens – adhering belt Desmosome (macula adherens) – spot attachment Gap junctions - communication Gap junctions - communication Gap junctions - communication Actin also interacts to some degree with the tight junction – maybe to position it? Classification of Epithelia Number of layers • Simple - one layer • Stratified - more than one layer Shape of superficial cells • Squamous - flat • Cuboidal - cube • Columnar – column Other • Pseudostratified - not truly stratified • Transitional - urinary tract Blood vessels Simple squamous Lens of eye Kidney Simple cuboidal Gallbladder Intestine Simple columnar Stratified Squamous Epithelium Nonkeratinized Stratified Squamous Keratinized Stratified Squamous SKIN CORNEA 111 Stratified Squamous SKIN Stratified Cuboidal in sweat gland ducts Stratified columnar = male urethra Pseudostratified Columnar epididymis Transitional Summary of Tissue Features of Epithelium • Avascular • Extraneous cells • Regeneration • Migration • Metaplasia • Basement membrane Secretion – active process consuming energy Exocrine glands - deliver their secretion into ducts opening into external or internal surface Endocrine glands ductless, deliver their secretions into the lymph or blood stream Pancreas exocrine endocrine Mechanism for Release of Secretory Products Merocrine secretion – exocytosis w/o loss of surface membrane Apocrine secretion – loss of part of apical cytoplasm and some plasma membrane Holocrine secretion – release of whole cell Cytocrine secretion – melanin granules transferred from melanocyte to keratinocytes Merocrine Apocrine Gland (endocrine) secretion effect Exocrine Glands Duct • Simple - unbranched duct • Compound - branched duct Secretory portion • Tubular • Coiled tubular • Branched tubular • Alveolar • Branched acinar • Tubuloacinar • Tubuloalveolar Mucus vs. serous Tubular Coiled tubular Branched tubular Alveolar Branched acinar Tubuloacinar Tubuloalveolar Summary Epithelium

Epithelium (One of Four Basic Types of Tissue)

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