Tissues and Histology: Epithelial (+ some intro)

Summer BIO 211 Key: CT = Connective tissue

tissues

•groups of cells that are similar in structure and function

types of tissues

epithelial, connective, nerve, muscle

epithelial

Forms boundaries between different environments, protects, secretes, absorbs, filters

ex of epithelial

skin surface (epidermis), Lining of GI tract organs

connective

supports, protects, binds other tissues together

ex of connective

bones, tendons, fat and other soft padding

nerve

Internal communication

ex of nerve

brain, spinal cord, and nerves

muscle

Contracts to cause movement

ex of muscle

skeletal muscle, cardiac muscle, smooth muscle

embryonic origins

All tissues in your body arise from these

how many types of embryonic layers are there

3

what are the 3 embryonic layers

ectoderm, mesoderm, endoderm

ectoderm

outer layer —> THINK: EctO → OUTer

what does the ectoderm turn into

Typically makes neural tissue —> nervous tissue

mesoderm

middle layer —> THINK: Meso → Midd

mesoderm turn into

Typically makes muscle tissue. THINK: Meso → Muscle

endoderm

inner layer THINK: Endo → INside

endoderm turn into

•Typically make epithelial tissue (though epithelial can arise from all three) THINK: Endo → INSIDES = linings → organs

epithelial tissue special characteristics

cellularity, special contacts, polarity, supported by CT, avascular, regenerative

cellularity

composed almost entirely of cells

special contacts

form continuous sheets held together by tight junctions and desmosomes

polarity

apical (top) and basal (bottom) surfaces

what supports the epithelial tissue

CT → reticular and basal laminae

what is interesting about epithelial with it being avascular

that it’s innervated

how is epithelia classified

based on the # of layers and the shape of the cell

simple

one layer

stratified

multiple layers

squamous

flat cell (tile like)

cuboidal

cube shape (square in simple)

columnar

tall rectangular

simple squamous

Single layer of flattened cells with disc shaped central nuclei and sparse cytoplasm

simple squamous function

•allows passage of materials by diffusion and filtration in sites where protection is not important; secrets lubricating substances in serosae

simple squamous location

kidney glomeruli, air sacs of lungs, lining of heart, blood vessels, lymphatic vessels, lining of ventral body cavity (serosae)

simple cuboidal

Single layer of cube like cells with large spherical central nuclei

simple cuboidal function

secretion and absorption

simple cuboidal location

Kidney tubules, ducts and secretory portions of small glands, ovary surface

simple columnar

•Single layer of tall cells with round to oval nuclei, many cells bear microvilli, some bear cilia. Layer may contain mucus secreting unicellular glands (goblet cells)

simple columnar function

Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus by ciliary action

simple columnar location (Nonciliated)

most of the digestive tract, gallbladder, and excretory ducts of some glands.

simple columnar location (Ciliated)

variety lines small bronchi, uterine tubes, and some regions of the uterus

pseudostratified columnar

•Single layer of cells differing in heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus secreting cells and bear cilia.

pseudostratified columnar function

•secrete substances, particularly mucus; propulsion of mucus by ciliary action

pseudostratified columnar location (ciliated)

variety lines the trachea and most of the upper respiratory tract;

pseudostratified columnar location (non-ciliated)

type in male sperm-carrying ducts and ducts of large glands.

stratified squamous

Thick membrane composed of several layers; surface cells are flattened (squamous) are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers

stratified squamous function

•protects underlying tissues in areas subjected to abrasion

stratified squamous location (nonkeratinized)

moist linings of the esophagus, mouth and vagina

stratified squamous (keratinized)

epidermis of the skin, a dry membrane

stratified cuboidal

quite rare and typically 2 layers thick

stratified cuboidal found

found in some sweat or mammary glands.

stratified columnar

limited distribution; Occurs at transition areas between two other types of epithelia

stratified columnar location

the pharynx, male urethra, and lining of some glandular ducts

transitional epithelia (resembles)

Resembles both stratified squamous and stratified cuboidal

transitional epithelium

basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch.

transitional epithelium function

stretches readily and permits distension of urinary organ by contained urine

transitional epithelium location

lines ureters, bladder, and part of the urethra

glandular epithelia: what is a gland

one or more cells that makes and secretes an aqueous fluid

glandular epithelia: site of product release

endocrine (ductless secreting hormones into the blood) or exocrine (secretes products via ducts to the surface or body cavities)

glandular epithelia: number of forming cells

relative # → unicellular or multicellular

what are goblet cells

These are unicellular exocrine gland cells that secrete mucous

what is mucous made by

mucins (proteins) in the rough ER → transported by vesicles from the golgi to the apical surface of the cell.

what does mucous protect against

pathogens and it also lubricates

merocine glands

secrete products by exocytosis

holocrine glands

entire secretory cell ruptures

what is the main method for goblet cells

merocrine method