General Histology Histos+logus= Histology (Science of tissues). - A cell is the basic unit of an organism. - A group of cells whether similar or different cells) may form a tissue. - A group of tissues may form an organ. A group of organs will establish a living organism (multicellular animals). Tissue: is groups of cells closely associated that have a similar structure and perform a related function Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Classification of cells Prokaryotic cell (prokaryote) A unicellular organism that lacks a membrane-bound nucleus (karyon), mitochondria, or any other membrane-bound organelle. The word prokaryote comes from the Greek (pro) "before" and κάρυον (karyon) "nut or kernel”. 2 domains, archaea and bacteria Ayoub Bazzaz, (BSc,MSc,PhD,DPSI) Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Eukaryotic Amoeba, Muscle cell In contrast, species with nuclei and organelles are placed in the domain Eukaryota. Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Comparison of eukaryotes vs. prokaryotes Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Cell division Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Cell division Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Tissue culture Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Key Terms Histology: the study of tissues. Tissues: Simply groups of similar cells that work together performing the same task Greatest form of teamwork in the body

Why Study Histology? Knowing the difference between normal and abnormal tissue is the first step in diagnosis and treatment of patients.

Tissues Four types of tissue Epithelial = covering Connective = support Muscle = movement Nervous = control Most organs contain all 4 types Connective tissue has non-living extra-cellular material [ECM] or (matrix) between its cells Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

4 Types of Tissue . Epithelium . Connective . Muscle . Nervous Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

* made of all four tissue types Skin, our largest organ * made of all four tissue types

Epithelial Tissue Makes up 3% of your body weight They don’t move They don’t send messages Their cells are all touching one another Of all tissues, they are the most widely varied in structure and function. All sit on a basement membrane.

Epithelial Tissues Sheets of cells Specialized contacts/cell junctions (see below) Basal lamina: protein scaffolding secreted by epithelial cells Basement membrane: reticular fibers (crossed collagen network) that supports epithelium--really associated connective tissue Connective tissue support Nutrients from capillaries in underlying connective tissue Nerves pass through Easily regenerates E.g. skin, lining of gut, mucous membranes Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Locations of Epithelial Tissues Covers the body (epidermis) Found on the inside of hollow organs and the outside of all organs Found above a connective tissue layer (epi = above) Lines the cavities, tubes, ducts, and blood vessels inside the body.

Epithelial Anatomy Apical surface – upper surface, is free or exposed to the “exterior” Basal surface – attached surface (below) Microvilli – small fingerlike extensions that increase the surface area allowing for more work to be done

Functions of Epithelial Tissue Protects from physical & chemical injury Protects against microbial infection Contains nerve endings which respond to stimuli. Filters, secretes & reabsorbs materials Secretes fluids to lubricate joints

Cell Organization Simple – single layer of cells; typically found where absorption and filtration occur or a single layer of epithelial is needed simple squamous simple cuboidal simple columnar Stratified – layers of cells; common in areas where protection is needed like the skin stratified squamous stratified cuboidal stratified columnar

Classes of Epithelia Simple: just one layer or cell shape Stratified: multiple layers and cell shapes Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Epithelial Tissue in Review…

Three Basic Shapes Squamous – like scales, or pancakes (“being squashed like a pancake”) Cuboidal – looks like cubes Columnar – longer and look like columns

Two Types of Stratified Columnar Ciliated Unciliated cilia No cilia

Squamous Epithelium Simple – one cell thick Forms solid layer of cells which line blood vessels, body cavities and covers organs in body cavities Stratified – multiple layers Forms epidermis

Cuboidal Epithelium Cuboid Cells Simple – one cell thick Roughly cube shaped Duct Line ducts in kidneys where re-absorption and secretion activities take place. Cuboid Cells Duct

Columnar Epithelium Simple – one cell thick Column shaped (long and narrow) Lines digestive tract where re-absorption & secretion occurs.

Confusing Epithelial Tissue Transitional Epithelium – stratified tissue that can’t make up its mind as to whether it is squamous or cuboidal Shape of cells depends upon the amount of stretching (urinary bladder)

Confusing Epithelial Tissue Continued… “Pseudostratified Columnar Epithelium” Looks like it has more than one layer because of the position of the nucleus Nuclei are positioned at differing levels Cells narrow in the area without nucleus

Types of Epithelial Membranes Mucous or mucosa– lining of tubes; moistens and protects from enzymes (stomach, trachea, and vagina) Serous or serosa – outside of organs; lubricates (all thoracic, abdominal and pelvic organs) Cutaneous or skin – body surface; protection Synovial – synovial joints; lines and protects synovial cavities (elbow, knee, hip, etc.)

Stratified Epithelia Squamous Transitional epithelium E.g. epidermis E.g. urinary structures--bladder Stretches from 6 cells to 3 cells thick as bladder fills and expands Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Quiz!! Can You Identify the Classes of Epithelium? E D A B C Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

1). limit the passage of molecules; Tight junctions: impermeable e.g. gut tube, doesn’t let enzymes from gut into blood stream. Tight junctions seal adjacent epithelial cells in a narrow band just beneath their apical surface. They consist of a network of claudins and other proteins. T.J. perform two vital functions: 1). limit the passage of molecules; 2). ions through the space between cells. Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Cell Junctions Desmosome: binding spots between cells with proteins called cadherins Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Desmosomes  Are intercellular junctions that provide strong adhesion between cells. Also link intracellularly to the intermediate filament cytoskeleton they form the adhesive bonds in a network that gives mechanical strength to tissues. Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Are tubes that let small molecules pass between cells. Gap junctions Are tubes that let small molecules pass between cells. Are a specialized intercellular connection between a multitude of animal cell-types. Directly connect the cytoplasm of adjacent cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells. Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Features of Lateral Surface of Epithelium Cells are connected to neighboring cells via: Proteins-link cells together, interdigitate Contour of cells-wavy contour fits together Cell Junctions Desmosomes-adhesive spots on lateral sides Tight Junctions-at apical area, plasma membrane of adjacent cells fuse, nothing passes Gap junction-spot-like junction occurring anywhere, lets small molecules pass Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Features of Apical Surface of Epithelium Microvilli: In small intestine Finger-like extensions of the plasma membrane of apical epithelial cell Increase surface area for absorption Cilia: Respiratory tubes Whip-like, motile extensions Moves mucus, etc. over epithelial surface 1-way Flagella: spermatoza Extra long cilia Moves cell Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Features of the Basal Surface of Epithelium Basal lamina: supportive sheet between epithelium and underlying connective tissue Selective filter Basement membrane = basal lamina plus underlying reticular fiber layer Attaches epithelium to connective tissue below Sometimes the two are used interchangeably Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Name that Epithelial Feature! (name and location on cell) 3 Cilia Tight junction Microvilli Basement membrane 3 1 1 2 2 4 4 Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

Glands: epithelial cells that make and secrete a water-based substance Exocrine Glands Secrete substance onto body surface or into body cavity Have ducts E.G., salivary, mammary, pancreas, liver Endocrine Glands Secrete product into blood stream Either stored in secretory cells or in follicle surrounded by secretory cells Hormones travel to target organ to increase response No ducts Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).

GLANDS A cell or an organ in human and animals that synthesizes chemical substances and secretes them for the body to use or eliminate, either through a duct (exocrine gland) or directly into the bloodstream (endocrine gland) Ayoub Bazzaz, (BSc,MSc,PhD,DPSI).