Histology Introduction PDF

Histology Introduction By MS.c. Azal Alsaoud Definition Histology is the science of the microscopic structure of cells, tissues and organs. It also helps us understand the relationship between structure and function of human being. Tissues Cells work together in functionall...

Histology Introduction By MS.c. Azal Alsaoud Definition Histology is the science of the microscopic structure of cells, tissues and organs. It also helps us understand the relationship between structure and function of human being. Tissues Cells work together in functionally related groups called tissues How is this done? Attachments communication Types of tissues: 1. Epithelial – lining and covering 2. Connective – support 3. Muscle – movement 4. Nervous – control Epithelial Tissue – General Characteristics & Functions Covers a body surface or lines a body cavity Forms most glands Functions of epithelium Protection Absorption, secretion, and diffusion Filtration Forms slippery surfaces (mucus secretion Special Characteristics of Epithelia Cellularity cells are in close contact with each other with little or no intercellular space between them Specialized contacts may have junctions for both attachment and communication Polarity epithelial tissues always have an apical and basal surface Support by connective tissue at the basal surface, both the epithelial tissue and the connective tissue contribute to the basement membrane Avascular nutrients must diffuse from basal layer Innervated Regenerative epithelial tissues are highly mitotic Classifications of Epithelia First name of tissue indicates number of layers Simple – one layer of cells Stratified – more than one layer of cells Classifications of Epithelia Last name of tissue describes shape of cells Squamous – cells wider than tall (plate or “scale” like) Cuboidal – cells are as wide as tall, as in cubes Columnar – cells are taller than they are wide, like column Naming Epithelia Naming the epithelia includes both the layers (first) and the shape of the cells (second) i.e. stratified cuboidal epithelium The name may also include any accessory structures Goblet cells Cilia Keratin Special epithelial tissues (don’t follow naming convention) Psuedostratified Transitional Simple Squamous Epithelium Description single layer of flat cells with disc-shaped nuclei Special types Endothelium (inner covering) slick lining of hollow organs Mesothelium (middle covering) Lines peritoneal, pleural, and pericardial cavities Covers visceral organs of those cavities Simple Squamous Epithelium Function Passage of materials by passive diffusion and filtration Secretes lubricating substances in serous membranes Location Renal corpuscles (kidneys) Alveoli of lungs Lining of heart, blood and lymphatic vessels Lining of ventral body cavity (serosae/serous memb.)  Simple Squamous Epithelium Simple squamous lining the walls of the capillary Simple Squamous Epithelium Simple Cuboidal Epithelium Description single layer of cube-like cells with large, spherical central nuclei Function secretion and absorption Location kidney tubules, secretory portions of small glands, ovary surface Simple Cuboidal Epithelium Simple Columnar Epithelium Description single layer of column-shaped (rectangular) cells with oval nuclei Some bear cilia at their apical surface May contain goblet cells Function Absorption; secretion of mucus, enzymes, and other substances Ciliated type propels mucus or reproductive cells by ciliary action Simple Columnar Epithelium Simple Columnar Epithelium Location Non-ciliated form Lines digestive tract, gallbladder, ducts of some glands Ciliated form Lines small bronchi, uterine tubes, and uterus Pseudostratified Columnar Epithelium Description All cells originate at basement membrane Only tall cells reach the apical surface May contain goblet cells and bear cilia Nuclei lie at varying heights within cells Gives false impression of stratification Function secretion of mucus; propulsion of mucus by cilia  Pseudostratified Columnar Epithelium Locations Non-ciliated type Ducts of male reproductive tubes Ducts of large glands Ciliated variety Lines trachea and most of upper respiratory tract Stratified Epithelia Contain two or more layers of cells Regenerate from below Major role is protection Are named according to the shape of cells at apical layer Stratified Squamous Epithelium Description Many layers of cells – squamous in shape Deeper layers of cells appear cuboidal or columnar Thickest epithelial tissue – adapted for protection Stratified Squamous Epithelium Specific types Keratinized – contain the protective protein keratin Surface cells are dead and full of keratin Non-keratinized – forms moist lining of body openings Function Protects underlying tissues in areas subject to abrasion Location Keratinized – forms epidermis Non-keratinized – forms lining of esophagus, mouth, and vagina Stratified Squamous Epithelium stratified columnar epithelium Stratified columnar epithelium is a rare type of epithelial tissue composed of column-shaped cells arranged in multiple layers. It is found in the conjunctiva, pharynx, anus, and male urethra. It also occurs in embryo. stratified cuboidal epithelium stratified cuboidal epithelium. Stratified cuboidal epithelia is a rare type of epithelial tissue composed of cuboidally shaped cells arranged in multiple layers. They protect areas such as ducts of sweat glands, mammary glands, and salivary glands. Transitional Epithelium Description Basal cells usually cuboidal or columnar Superficial cells dome-shaped or squamous Function stretches and permits distension of urinary bladder Location Lines ureters, urinary bladder and part of urethra Transitional Epithelium