Histology Theory 1 PDF

Lec 1 Histology Dr.Reshna Kamal Albarzanji [email protected]  HISTOLOGY Histology is the study of the body tissues and how these tissues are arranged to constitute organs. Tissue is a group of similar cells, specialized in a common direction and set apart for the p...

Lec 1 Histology Dr.Reshna Kamal Albarzanji [email protected]  HISTOLOGY Histology is the study of the body tissues and how these tissues are arranged to constitute organs. Tissue is a group of similar cells, specialized in a common direction and set apart for the performance of a common function. Tissue are groups of cells with a common structure and function. Different types of tissue have different structures that are especially suited to their functions. The purpose of studying histology: 1-understanding tissue structure at level not visible within eye. 2- understanding the relationships between tissue structure and functions. 3- understanding the differences between normal & abnormal structure in histopathology learning.  Tissue The human body is composed of four basic types of tissues: 1-Epithelial tissue 2-Connective tissue 3-Muscular tissue 4-Nervous tissue. — In association with one another form different organs & system of the body. 1- Epithelial tissue. Epithelium- is a layer of cells that forms a barrier with specific properties. — Specific properties of epithelium: 1. A free surface exposed to the environment or to some internal chamber or passage way. 2. Attachment to underlying connective tissue by basement membrane. 3. The absence of blood vessels. Because of this a vascular condition, epithelial cells must obtain nutrients from deeper tissues or from their exposed surface. — Name the epithelial tissue found in each of the locations: — 1-lining Bowman's space in the cortex ----- — 2-stomuch — 3-ureters — 4-lines the ovary — 5-Ducts of sweat glands — 6- thyroid gland follicles — 7-endothelium — 8-nasal cavity — 9-esophagus — 10-tubules in the kidney 4- Cells packed closely together often specialized junctions between cells with little ECF = Extra Cellular Fluid. 5- High rate of mitosis and regeneration. 6- all epithelial cells are derived from the (3) embryonic germ layers, the epithelial lining of skin, mouth, nose & anus are derived from the ectoderm, the epithelium of digestive tract & respiratory are derived from the endoderm, while the epithelia lining blood vessels are derived from the mesoderm. 7- epithelial tissues are continuously renewed tissues. the main functions of the epithelial tissues are : 1- Covering & lining. (covers both external and internal body surfaces. Also covers the skin, lines internal passageways that communicate with the outside world, such as the digestive, respiratory, reproductive and urinary tract). 2-Control permeability, absorption & secretion. 3- Secretion produce specialized secretions (glands). 4- Sensation (Neuroepithelium). 5-Contractility. 6- Protection. Classification of epithelial tissues: 1- shape of the cells at the free surface : a- Squamous: flat. b- Cuboidal: square. c- Columnar: tall. 2- number of cell layers of the epithelial membrane a-Simple: one layer of cells. b-Stratified: more than one layers of cells. 3-function A-Covering and lining Epithelia. b-Glandular epithelia. A- Simple epithelium: Simple epithelia consist of a single layer of cells. — Simple epithelia can be divided according to the morphology of the cells into : — 1- simple squamous epithelium. Single layer of flattened cells with disc shaped nuclei and sparse cytoplasm. — -Location: lining Bowman's space in the cortex of the kidney. lining body cavity (mesothelium), cardiovascular and lymphatic systems, surface of lung and kidneys (gas and liquid exchange) lines blood vessels (endothelium) — function = — diffusion and filtration  peritoneum Lung alveoli , Endothelial cell (simple squamous) capillary Endothelial cell lumen Blood capillary Simple squamous epithelium lining Bowman's space in the cortex of the kidney. — 2-Simple cuboidal epithelium Simple cuboidal epithelium is formed by a single layer of cuboidal cells (roughly square in shape when cut in cross section). Locations — 1-lines most of the tubules in the kidney, — 2-lines the excretory duct and forms the secretory portion of many glands, and lining many ducts and tubules of the body. — 3-lines the ovary. Functions secretion and absorption. 3-Simple columnar epithelium — Consists of a single layer of cells that are taller than they are wide. — their nuclei typically lie in the basal portion of the cell and form a single line in cross section. Locations — -found lining the stomach, intestines, and some large ducts in the body. often have surface modifications such as cilia and microvilli — function secretion and — absorption. Simple Columnar Epithelium: Figure 4.2c 4-Pseudostratified Columnar epithelium — Single layer of cells with different heights; all touch the basal lamina but some do not reach the free surface, Nuclei are seen at different layers. — Locations — 1-lines most of the nasal cavity, trachea, bronchi. — 2-lines some of the male reproductive tract. Functions — protection, secretion, and the movement of — substances (mucus) over — The surface by cilia.  Pseudostratified Columnar Epithelium — Single layer of cells with different heights; some do not reach the free surface — Nuclei are seen at different layers — Function in secretion and propulsion of mucus — Present in the male sperm-carrying ducts (nonciliated) and trachea (ciliated) Figure 4.2d — STRATIFIED EPITHELIA — Stratified epithelia consists of two or more cell layers. — Subtypes are named according to the shape of the surface cells alone. — 1-Stratified Squamous Epithelium – Is composed of many layers of cells with squamous cells on the surface. The middle are cuboidal while the basal cells that resting on a basal lamina are columnar, this types occurs in two forms are : 1-Stratified Squamous Keratinized epithelium. 2-Stratified Squamous non- Keratinized epithelium. — Locations 1– Keratinized stratified squamous epithelium is located in the skin (epidermis). 2– Nonkeratinized stratified squamous epithelium locations include: lining of the oral cavity, esophagus, anus, and vagina. Functions: The major function of stratified squamous epithelium is protection of underlying areas. The keratinized variety of the epidermis also protects the body from water loss. Stratified squamous epithelium Stratified squamous epithelium (cornea) (wall of vagina) 1-Stratified Squamous Keratinized epithelium (epidermis) 2-Stratified Cuboidal Epithelium: Quite rare in the body. Typically two to three cell layers thick only top layer is cuboidal. Locations Testis tubules; vesicular (Graafian) follicles of ovary. Ducts of sweat glands; sebaceous glands. Intermediate zones of some regions, such as the urethra and conjunctiva. — Functions Protection, Secretion and absorption  Stratified cuboidal epithelium (lactiferous duct of breast) Ducts of sweat glands — 3-Stratified Columnar Epithelia: — Limited distribution in the body resembles stratified cuboidal epithelium, but its superficial cells are columnar and may be ciliated. — Locations — Pharynx (in part); larynx (in part); Urethra (in part); Excretory ducts of salivary and mammary glands (in part), and lining some glandular ducts. Stratified Columnar Epithelium 4-Transitional Epithelia Several cell layers, basal cells are cuboidal surface cells are dome shaped (or flat) surface cells are large and often bi-nucleated Stretches to permit the distension of the urinary bladder Locations: Lines the urinary bladder, ureters, and part of the urethra. When the bladder is empty, the surface cells appear domelike, when the bladder is full, the surface cells flatten. Function: Stretches readily and permit destination of urinary organs  Transitional Epithelium — Several cell layers, basal cells are cuboidal, surface cells are dome shaped — Stretches to permit the distension of the urinary bladder — Lines the urinary bladder, ureters, and part of the urethra Figure 4.2f