Introduction to Basic Histology PDF

Introduction to Basic Histology Dr. hiba mohammed suliman  HISTOLOGY Study of tissue of the organ system Or Microscopic anatomy HISTO-PATHOLOGY looks for tissue changes that indicate disease Cell Specialization Multicellularity requires a distr...

Introduction to Basic Histology Dr. hiba mohammed suliman  HISTOLOGY Study of tissue of the organ system Or Microscopic anatomy HISTO-PATHOLOGY looks for tissue changes that indicate disease Cell Specialization Multicellularity requires a distribution of work Cells look and function differently (specialize) in different parts of the body (ex. bone cell vs. nerve cell) Cells specialize into types of tissues, then form organs. Bodies of vertebrates are composed of different cell types -Humans have 210 Page 4  Types of Tissues: Tissues a group of cells with a common embryonic origin performing a similar function  Function together to carry out specialized activities. Tissue components : Cells and Extracellular Matrix Extracellular matrix (ECM) consists of many molecules, which are highly organized and form complex structures like collagen fibrils and basement membranes. ECM functions: A. To furnish mechanical support for the cells, B. To transport nutrients to the cells, and C. To carry away catabolites and secretory products. Note: Cells not only produce extracellular matrix components but are also influenced by them creating an intense interaction between cells and matrix.
 Embryonic Tissue Various adults tissues are derived from these three embryonic tissues (3 major germ layers ) that form the embryonic disc (source of stem cells) Endoderm Inner layer Forms lining of digestive tract and derivatives Mesoderm Middle layer Forms tissues as such muscle, bone, blood vessels Ectoderm Outer layer Forms skin and neuroectoderm  Cellular Differentiation A different set of genes gets activated in each cell type, so each cell type produces a different set of proteins The different proteins give the different cell types their characteristic structural and functional properties  Types of Connections 1. Gap Junction: two cells held together by interlocking membrane proteins (channel proteins). allows for narrow passageway of solutes and ions; in cardiac & smooth muscle 2. Tight junction: outermost lipid layers of adjacent cell membranes are tightly pressed together by interlocking proteins. prevents passage of water and solutes – found in digestive tract & stomach keeping harsh chemicals from damaging basic tissue 3. Desmosomes two cell membranes locked together by intercellular cement and a network of fine protein filaments. very strong, resist stretching and twisting; found in skin Intercellular connections 
Primary Tissue Types
(Derived from the Embryonic Tissue)

Epithelium…covering Connective tissue…support Muscle tissue…movement Nervous tissue…control Integration of Tissues Small intestine as an example. Cavity (lumen) with food. Epithelium for lining  secretion and absorption. Muscle for moving food. Connective tissue to join. Nerves (not seen). Epithelium tissue Epithelial Tissue Epithelial tissues are composed of closely aggregated cells of a similar type tightly adhered to each other, with very little extracellular substance. General Characteristics : Epithelium has complex embryological origins derived from all three germ layers. ectoderm - surface of body (epidermis) mesoderm - body cavity lining (mesothelium), blood vessel lining (endothelium). endoderm - digestive tract lining, lungs, liver. The epithelial tissue, or epithelium, consists of sheets of cells that covers a surface or lines a cavity or forms a gland. The epithelial cells rest on a basement membrane which may be clear or not clear. Absence of nerves (except for a few axons in the deeper layers). Avascular – no blood vessels — nutrition is by diffusion from the highly vascular connective tissue (known as the lamina propria) underlying all epithelia Epithelium has a little intercellular substance. Epithelium (note avascular condition) Diffusion of O2 and CO2 Capillary Functions: (e.g. skin, intestines) 1. Protection 2. Sensation (e.g. gustative and olefactory neuroepithelium). 3. Secretion (e.g. glands). 4. Absorption (e.g. intestines). 5. Excretion (e.g. kidney and sweat glands). 6. Diffusion (e.g. walls of capillaries and lungs) 7. Cleaning (e.g. air passages trachea and nose ) 8. Reduces Friction (e.g. epithelial cells that line the entire circulatory system reduce friction between the blood and the walls of the blood vessels. ) 9. Contractility (e.g. myoepithelial cells). Classification of Epithelia Terms that help us understand what kinds of tissues we are identifying: Terms referring to the layers Simple = one layer Stratified = more than one layer Pseudostratified = false layered (appears to be more than one layer, but only one); ciliated = with cilia Terms referring to the cell shapes Squamous = flat Cuboidal = cube Columnar = rectangular (column) Transitional = ability to change shape Classes of Epithelia Based on shape and the layers Table 4–1 
Simple Epithelium

Types of simple epithelium: Simple squamous epithelium Cuboidal epithelium Simple columnar epithelium (non-ciliated and ciliated) Pseudostratified columnar epithelium (non-ciliated and ciliated)  Simple Epithelium: 1. Squamous Epithelium: Nucleus is centrally located and appears flattened oval or sphere. Cells in direct contact with each other Locations: They form the lining bod y cavities such as the mouth, blood vessels, hear t, C apillary walls, alveoli of the lungs, covering visceral organs. Function: diffusion, f il tration, absorption, and secretion. They make up the outer layers of the skin.  Simple Epithelium -Squamus Simple squamous epithelium lining Bowman's space in the cortex of the kidney. SIMPLE EPITHELIUM -SQAUMOUS 2- Simple Cuboidal Epithelium: Cuboidal shaped cells Cell nuclei round and centrally located Locations: lining kidney tubules, salivary ducts, pancreatic ducts
Function: diffusion, filtration, absorption, and secretion Examples:  Walls of kidney tubules: absorption of substances from filtrate & secretion of substances into filtrate.  Glands: secretion of products made by the glandular cells  Cuboidal Cell Spherical, large nuclei LUMEN Basement Apical surface membrane 3- Simple Columnar Epithelium:  Column shaped cells (cells are elongated).  Oval nuclei at near base of the cells.  Some columnar cells are specialized for sensory reception such as in the nose, ears and the taste buds of the tongue.  Goblet cells (unicellular glands) are found between the columnar epithelial cells of the duodenum. They secrete mucus or slime, a lubricating substance which keeps the surface smooth.  They have two type: a)ciliated simple columnar : Columnar epithelial cells with cilia at the apical surface b)non-ciliated simple columnar :Contains columnar cells with microvilli at their apical surface and goblet cells  3- Simple Columnar Epithelium: Locations:  Digestive tract lining, respiratory, reproductive and urinary tracts. Function:  (diffusion, filtration, absorption, and secretion protection).  goblet cells which can be found among columnar cells Secreted mucus serves as oiling for the lining of digestive, respiratory, reproductive and urinary tracts. Examples:  Lines the uterus, stomach, & intestines: where it protects underlying tissues  Lining of stomach & intestine : secretion of digestive juices, have microvilli for absorption (Absorbs nutrients).  In the intestine: simple columnar epithelial cells possess microvilli that increase the surface area available for absorption  Uterine tubes: cilia to help egg move to uterus  Central canal of spinal cord: cilia move the Cerebrospinal fluid (CSF).  In respiratory tract, Secreted mucus on the surface traps inhaled foreign particles. Beating cilia moves particles to the throat for removal by coughing, swallowing, or sneezing Note (The cilia also prevents the destruction of the stomach lining by acidic gastric juices). Simple Columnar Epithelium Cells of simple columnar epithelium show specialisations suited to function. Cells of simple columnar epithelium show specialisations suited to function. Absorption Microvilli (Brush Border) Secretory “vesicles” Golgi rER Individual microvilli are too fine Secretion to be seen with the light microscope. With the LM, one sees only a pink band on the surface Simple Columnar Epithelium Cilia Hairlike, motile Each cilium based by a basal body. For movement of fluid on the surface. Fluid may be watery or viscous (mucus). Cilia “beat” in one direction. Stages in the functional cycle of a mucus producing goblet cell. Simple columnar epithelium Copyright 2009, John Wiley & Sons, Inc. Simple Columnar Epithelium CILIATED COLUMNAR 4- Pseudostratified columnar epithelium:  This type consists of one layer of columnar cells which press on each other. All remain attached to the basement membrane.  looks like columnar epithelium only it has different nuclear layers. Some cells have a centrally located nucleus while others have a basal nucleus. Ciliated cells secrete mucus and bear cilia Non-ciliated cells lack cilia and goblet cells Locations:  Covering the internal surface of the nasal septum, trachea, bronchi Function:  protection, secretion Examples:  Lining of nasal cavity, trachea, and bronchi: secretion of mucus by goblet cells which provide protection against dust particles in respired air. Their cilia paralyzed as a result of smoking-Nicotine. (trap and move foreign particles to the mouth).  Stratified Epithelium  The term “stratif ie d” refers to the layered arrangement of cells (Two or more layers of cells).  Specif ic kind of stratif ied epithelium depends on the shape of cells in the apical layer. Stratified squamous epithelium Stratified cuboidal epithelium Stratified columunar epithelium Transitional epithelium  Stratified Squamous Epithelium
 Several layers of cells that are flat in the apical layer New cells are pushed up toward apical layer As cells move further from the blood supply they dehydrate, harden, and die.  The outer layers of cells appear f lat, but the inner cells vary in shape from cuboidal to columnar.  Stratif ie d squamous epithelium serves as a barrier to the outside environment in locations such as the skin, mouth, and esophagus.  Have two type:  Keratinized form contain the fibrous protein keratin Found in superficial layers of the skin  Non-keratinized form does not contain keratin Found in mouth and esophagus Stratified Squamous Epitheluim (Keratinized) keratin S qu a mou s Cuboidal Columnar Basement Membrane Dense-Irregular Connective Tissue Stratified Squamous Epitheluim (Keratinized) Stratified Squamous Epitheluim (Non keratinize d) Stratified Cuboidal Epithelium  This type of tissue is relatively rare in the human body.  cube-shaped  commonly cells make up two layers Location lining a lumen of :  sweat glands in the skin  mammary gland in the breast  salivary glands in the mouth  may be active (pump material in/out of lumen). Functions :  protection of larger ducts - cell layers surround/protect gland ducts Stratified Cuboidal Epithelium Stratified Cuboidal Epithelium  Stratified columnar epithelium  rare  Columnar cells in apical layer only  Basal layers has shorten, irregular shaped cells Location  often found between simple columnar epithelia and stratified squamous epithelia  found near salivary glands - cell lining protects the salivary duct, goblet cells found between the cells  found in vas deferens where it protects and aids in secretion of glands.  also form layers in ocular conjunctiva and the linings of the pharynx, anus, uterus, urethra Functions  secretion and protection Examples:  intestinal lining - ciliated to help move nutrients and increase absorption, also protects against pathogens/bacteria Stratified Columnar Epithelium stratified columnar epithelium  Transitional Epithelium  (special type of stratified sheet epithelium)  Variable appearance (Shape of cells depends upon the amount of stretching)  In relaxed state, cells appear cuboidal  Upon stretching, cells become flattened and appear squamous Location:  Found in the urinary system and urethras. Function:  elasticity: stretch and retract.  Found in urinary bladder to keep urine from diffusing back into the internal cavity 
Transitional Epithelium

Transitional Epithelium
Glandular epithelium  Cells that secrete or export a product.  Secretion = protein, lipids, hormones, steroids, acids Endocrine glands (internally secreting) No duct, release secretion into blood vessels Often hormones Thyroid, adrenal and pituitary glands Function in maintaining homeostasis Exocrine glands (externally secreting) Contain ducts, empty onto epithelial surface Sweat, Oil glands, Salivary glands, Mammary glands. Structural Structural Classification of Exocrine Glands Classification of Exocrine Glands  Branching  Simple – single, unbranched duct  Compound – branched.  Shape: tubular or alveolar  Tubular – shaped like a tube  Alveolar – shaped like flasks or sacs  Tubuloalveolar – has both tubes and sacs in gland Shapes of Exocrine glands Modes of Secretion in Glandular Epithelia 1. Merocrine secretion  Is produced in Golgi apparatus  Is released by vesicles (exocytosis)  For example, sweat glands MODES OF SECRETION IN GLANDULAR EPITHELIA 2. Apocrine secretion  Is produced in Golgi apparatus  Is released by shedding cytoplasm  For example, mammary gland  MODES OF SECRETION IN GLANDULAR EPITHELIA 3. Holocrine secretion  Is released by cells bursting, killing gland cells  Gland cells replaced by stem cells  For example, sebaceous gland inside of hair follicles Holocrine Glands: Arrangement of cells Unicellular: Goblet cells Multicellular: Tubular – Brunner’s gland in duodenum Alveolar – Sebaceous/Oil glands Combination – Salivary glands Mucous = mucin: A glycoprotein that combines with water Thank Thank you you