test bio normal

Histology

study of tissues

How are tissues classified?

cell structure, composition of noncellular extracellular matrix and cell function

types of tissues

epithelial, connective, muscle and nervous

extracellular matrix

material found outside of cells. Gives support , structure and helps cells stick together

Blast

create the matrix

cytes

maintain the matrix

clast

breaks matrix down for remodeling

Epithelial tissue characteristics

mostly composted by cells, very little extracellular matrix

Covers body surfaces and forms glands:

-Outside surface of the body

-lining of digestive, respiratory and urogenital systems

-heart and blood vessels

- linings of many body cavities.

Avascular ( materials must muve by diffussion from underlying connective tissue)

high regeneration capacity.

epithelial tissue functions

protecting underlying structures

Barrier action ( skin)

allowing transport of substances

Secreting and absorbing substances

Classification of epithelial tissues

number of layers:

simple - 1 layer ( all cells touch BM)

Stratified- multiple layers

Pseudostratified - it looks it has multiple layers but it only has one

Transitional- multiple layers with cells that stretch and relax( changing its shape)

Classification of epithelial tissues

Cell shape:

Squamous - flat

Cuboidal- cube/ box

Columnar- rectangular column

Simple Squamous Epithelium

Single layer of flat, hexagonal cells

Functions: diffusion, filtration,secretion, protection against friction

Location: lining heart and blood vessels, lymphatic vessels, alveoli of the lungs, parts of kidney tubules, lining of serous membranes of body cavities.

Simple cuboidal epithelium

Single layer of cube-shaped cells with round central nucleus

Functions: secretion ,absorption, protection

Location: small glands, kidney tubules,surface of ovaries, terminal bronchioles of lungs.

Simple Columnar Epithelium

Single layer of tall, narrow cells, some cells have cillia ( bronchioles of lungs, auditory tubes, uterus, uterine tubes) or microvilli(intestines)

Functions: movement of particles out of the bronchioles of the lungs, movement of oocytes through uterine tubes( partial), secretion, absoption.

Location : Glands, some ducts, stomach, intestines (Absorption) ( these are for secretion), uterine tubes, uterus, bronchioles of the lungs, bile ducts, ventricles of the brain,auditory tubes, gallbladder.

Stratified squamous epithelium

multiple layers, bottom cells are cube - shaped and top cells are flat

2 types of tissue :

- non-keratinized: surface cells are alive and moist. Location: mouth , throat, esophagus, anus, vagina, urethra.

- keratinized: surface cells fill with keratin and die ( tougher cells). Location: skin

Function: protect body by resisting friction, prevent infection, reduce water loss.

Stratified cuboidal epithelium

multiple layers of somewhat cube - shaped cells.

Function: secretion, absorption, protection against infection.

Location: sweat gland ducts, ovarian folicular cells, salivary gland ducts.

Stratified columnar epithelium

Multiple layers of tall, thin cells resting on layers of cubed- shaped cells, the cells are cilliated in the larynx.

Function: protection and secretion.

location: mamary gland ducts, larynx, a part of male urethra.

Pseudostratified columnar epithelium

single layer with appareance of multiple layers. Cells with different heights ( nuclei appears at different levels. Most of these cells have cillia on top and include globet cells ( make mucus).

Function: produce and move mucus, which traps germs and dust, clearing them from the airways.

Location. lining the nose, sinuses, ear tubes, throat, trachea and bronchi of lungs.

transitional epithelium

Stratified cells that look cuboidal when the organ is relaxed and squamous when the organ stretches by fluid. ( changes shapes)

Function: allows organs stretch and hold urine without leaking

Location: lining of the urinary bladder, ureters, upper part of urethra.

Free surface modifications

Microvilli

increase surface area of absorption or secretion

Free surface Modifications

Cillia

move mucus across surface of cells

Cell Connections

Location: lateral and basal surfaces of cells.

Functions: make permeability layer, bind cell together, provide mechanism for intercellular communication

types : desmosomes and hemidesmosomes, tight junctions, adhesion belt, gap junctions

Glands

formed by infolding of epithelium.

Endocrine: no open contact with exterior, no ducts. Many different blood vessels. Produce hormones

Exocrine: open contact with exterior by ducts that open to the free surface of epithelium. Classified by structure of the duct, structure of secretory portion and method of secretion

classification by structure

Unicellular: single cell ( globet cell)

Multicellular: many cells

-Simple glands: duct does not branch

-Compound glands: duct branches.

Classification by structure of the secretory portion

• Tubular: tube - shaped

• Alveolar: rounded like a sac ( burrata supermarket

• Tubuloalveolar: tubular and sac - shaped.

Classification by methods of secretion

Merocrine: exocytosis ( most common type)

Apocrine: pinched off parts of gland cells ( mamary glands and ceruminous glands) .

Holocrine: shedding of cells ( sebaceous glands)

Connective Tissue

Cells separated by extracellular matrix

Abundant ( every organ)

a lot of types and functions

Functions of connective tissue

Enclose ( cover) organs and separate organs into layers

Connects tissues ( tendons and ligaments)

Support and movement ( bones )

Storage ( fat)

Cushion and insulate ( fat)

Transport( blood)

Protect ( cells of immune system)

Cells of Connective tissue

Osteoblasts form bone, osteocytes maintain it and osteoclasts break it down

Chondroblasts form cartilage and chondrocytes maintain it.

Fibroblasts form fibrous connective tissue and fibrocytes maintain it

Cells of connective tissue

Adipose or fat cells ( adipocytes): common in some tissues( dermis ), rare in some( cartilage)

Mast cells: common beneath membranes and along small blood vessels. Important for inflammation, releases heparin, histamine and proteolytic enzymes ( for injuries).

White bloood cells( leukocytes): respond to injury or infection

Macrophages: phagocytize to give protection against foreign and injured cells

- Fixed: same position

-Wandering: move by amoeboid movement

Cells of connective tissue

Platelets: pieces of hematopoletic cells involved in clotting

Undifferentiated mesenchyme( stem cells): can change into different types of adult cells