Epithelium 1: Epithelial Cells Flashcards
What are the types of tissue?
Epithelial
Connective
Muscle
Nervous
What are the general characteristics of epithelial tissue?
Covers and lines organs/cavity walls
Forms boundaries
What are some special characteristics of epithelial tissues?
Free surface open to the outside or an open internal space
Basement membrane anchors epithelium to underlying connective tissue
Lack blood vessels
Readily divide (ex. skin healing)
Tightly packed with little extracellular space
What is the basement membrane?
Layer of connective tissue on which epithelial cells lie
How is the basement membrane formed?
Recticular lamina (on which epithelial cells lie) bound to areolar connective tissue
What are the two types of epithelial tissue?
Epithelia: Layers of cells covering internal/external surfaces
Glands: Produce secretions
How can epithelia be classified?
Shape:
1. Squamous: Thin, flat cells
2. Cuboidal: Cube-shaped cells
3. Columnar: Tall, elongated cells
Number:
1. Simple: Single layer
2. Stratified: Two or more layers
Characteristics of Simple Squamous Epithelium
Cells are flat and thin
Flattened nuclei
Helps in diffusion of gases and nutrients
E.g., endothelium, mesothelium, epithelium of the alveoli
Characteristics of Simple Cuboidal Epithelium
Height and width of the cell is equal
Nucleus is rounded
E.g., covering of ovary, lining of ducts, thyroid follicles
Characteristics of Simple Columnar Epithelium
Height of the cell more than its width
Elongated oval nuclei
Eg : digestive tract (stomach, small intestine, large intestine)
What are characteristics of stratified epithelium?
Multilayered
Resistant to wear and tear
What are the types of stratified epithelium?
Stratified squamous non-keratinized
Stratified squamous keratinized
Stratified cuboidal
Stratified columnar
Transitional
Layers of Stratified Squamous Non-Keratinized Epithelium
Basal columnar cells
3-4 layers of polyhedral cells
Surface layers of squamous cells
E.g., oral cavity, esophagus, anus and vagina
Layers of Stratified Squamous Keratinized Epithelium
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Stratum Basale: Basal columnar cells
Stratum Spinosum: 3-4 layers of polyhedral cells
Stratum Granulosum: Surface layers of squamous cells
Stratum Lucidum: Homogenous stratum, cells with indistinct cell boundaries
Stratum Corneum: Dead cells or keratin
E.g. skin
Characteristics of Stratified Cuboidal Epithelium
Required for protection, absorption and secretion
Found in lining of some ducts, e.g. sweat glands
Characteristics of Stratified Columnar Epithelium
Required for protection
Found in small areas of phraynx, epiglottis, anus, mammary glands, salivary gland ducts and urethra
Layers of Transitional Epithelium/Urothelium
Basal columnar cells
3-4 layers of pear shaped cells
Topmost layer of facet cells (umbrella shaped)
Easily compressed under pressure
E.g., urinary bladder, ureter
Characteristics of Pseudo-Stratified Ciliated Columnar Epithelium
Single layer of columnar cells appears to be 2 layered
Cells are at different layers, only few reach the lumen
Nuclei are also at different levels and hence looks stratified
Only types with cilia on their surfaces
E.g., respiratory tract, trachea
