Dr Narmeen S. Ahmad Lab 1 1
Tissues are groups of cells with a common structure (form) and function (job). There are (4) types of tissue: 1. Epithelial 2. Connective 3. Muscle 4. Nervous 2
Epithelial cells Epithelium is an avascular tissue. The locations of epithelial cells: Cover the exterior body surfaces line internal closed cavities (including the vascular system) Found in body tubes that communicate with the exterior (the alimentary, respiratory, and genitourinary tracts). Found in glands and their ducts. 3
Feature of epithelial cells Packed and contiguous cells Little or no intercellular materials Cells are usually joined by a cell-to-cell junction. They are upon Basement membrane It separate epithelial cell and Connective tissue. It is non cellular membrane (proteinpolysaccharide rich membrane). 4
Feature of epithelial cells They have Microvilli Micorvilli are finger like cytoplasmic projections on the apical surface of most epithelial cells. 5
Feature of epithelial cells They bear Cilia on their free surface. Cilia are cytoplasmic and plasma membrane projection from apical surface Ciliated epithelial cells are found in respiratory system and fallopian tube. Cilia Epithelial cell 6
Feature of epithelial cells Some of epithelial cell covered by keratinized layers. Keratinization: The process in which the cytoplasm of the outermost cells of the mammalian epidermis is replaced by keratin. Keratinized layers protect underlying tissues. 7
Classification of Epithelial cells cells are classified into three main cell groups according to their shapes: 1. squamous (flat platelike) 2. cuboidal (height and width similar) 3. columnar (height 2 5 times greater than width) 8
Classification of Epithelial cells Depending on the layers, cell are classified into 1. One layer: simple epithelium 2. More than one layer: stratified epithelium Pseudostratified = false layered (appears to be more than one layer, but it is one layer). Pseudostratified 9
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1- Simple squamous epithelium Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia. They form the lining of cavities such as the kidney, blood vessels, and lungs. Function: Diffusion 11
endothelium The entire vascular system is lined with a simple squamous epithelium. However, here it is called endothelium. 12
2- Simple cuboidal epithelium As their name implies, cuboidal cells are roughly square or cuboidal in shape with central rounded nuclei. Present in kidney, ovary, testes, glands and ducts of glands. Function: secretion, and absorption 13
Cortex Medulla Glomerulus Tubule Simple squamous Ep. kidney tubules are lined by a simple cuboidal epithelium Simple cuboidal Ep. 14
Simple cuboidal epithelial cell are found on the surface of ovary 15
Simple cuboidal epithelium (ducts in Pancreas) 16
3- Simple columnar epithelium Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus- secreting unicellular glands (goblet cells). Location: o Non ciliated type lines most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands. o ciliated variety lines nose and fallopian tube. Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action. 17
Non ciliated Simple columnar epithelium 18
Ciliated simple columnar epithelium 19
4- Pseudostratified columnar epithelium Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia. Location: lines the trachea, most of the upper respiratory tract. Function: Secretion, particularly of mucus; propulsion of mucus by ciliary action. 20
Ciliated-pseudostratified columnar epithelium 21
5- Stratified squamous epithelium Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous). Location: Non-keratinized type forms the moist linings of the esophagus, mouth, and vagina. keratinized variety forms the epidermis of the skin Function: Protects underlying tissues in areas subjected to abrasion. 22
Stratified squamous non-keratinizing (vagina) 23
Stratified squamous keratinizing (skin) 24
6- Stratified cuboidal epithelium It is a type of epithelial tissue composed of multiple layers of cubeshaped cells. Only the most superficial layer is made up of cuboidal cells, and the other layers can be cells of other types. Location: lining the ducts of glands (e.g. sweat gland). Function: protection 25
Stratified cuboidal epithelium (Sweat gland ducts) 26
7- Stratified columnar epithelium It is a rare type of epithelial tissue composed of column shaped cells arranged in multiple layers. Location: found in the male urethra and large duct of some gland Function: protection Stratified Columnar Epithelium (urethra) 27
8- Transitional epithelium Transitional: ability to change shape varies between cuboidal and squamous depending on the degree of stretching. As the bladder, (or the ureters), fills with urine, the epithelium stretches, becoming thinner and the surface layer of cells takes on a squamous, rounded shape. These cells are called umbrella cells because of their characteristic shape, and you can use this feature to identify a transitional epithelium. 28
Transitional Epithelium (relaxed -top layer of cells is cuboidal) basement membrane basement membrane Transitional Epithelium (stretched-top layer of cells is squamous) 29
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The integumentary system consists of: 1.Skin 2. Appendages Nail Hair Sweat gland Sebaceous gland Integument = skin 31
Skin layers Three distinct regions Epidermis (Epithelial cells) Dermis (Connective tissue) Hypodermis (fatty layer) 32
Epidermis *Epidermis composed of stratified squamous epithelium Four types of cells are found in Epidermis: Keratinocytes produce keratin (tough fibrous protein) Melanocytes make dark skin pigment melanin Merkel cells associated with sensory nerve endings Langerhans cells macrophage-like dendritic cells Layers of Epidermis: Stratum Corneum (uppermost) Stratum Lucidum Stratum Granulosum Stratum Spinosum Stratum Basale (innermost) 33
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Epidermis and dermis of (a) thick skin and (b) thin skin 35
Dermis It is strong, flexible connective tissue Fibroblasts, macrophages, mast cells, WBCs are found in dermis. It contains nerves, blood vessels, hair follicle, and glands. 36
Hypodermis Masses of loose connective and adipose tissues A major function of the subcutaneous tissue is to connect the skin to underlying tissues such as muscles 37
Skin appendages Derived from epidermis but extend into dermis Include Hair and hair follicles Sebaceous (oil) glands Sweat glands Nails 38
Hair follicle Parts of hair: Hair root Hair shaft (projecting above epidermis) Structure of hair: Medulla Cortex Cuticle Each hair on your body grows from a hair follicle (folding of epidermal surface into dermis): Hair bulb: expansion of follicle aroud hair root. Papilla: contain blood supply. Matrix: produces the actual hair shaft Connective tissue: wall of hair follicle 39
Matrix Papilla Hair bulb 40
Nail >Nail root > Nail Plate > Nail bed > cuticle > nail wall > Hyponychium 41
Sebaceous (oil) glands Entire body except palms and soles Produce sebum by holocrine secretion. 42
Sweat glands It is a small gland that secretes sweat, situated in the dermis of the skin. Such glands are found over most of the body. 43
Functions of skin Protection Synthesizes vitamin D Regulates body heat Prevents unnecessary water loss Sensory reception (nerve endings) 44