Lecture 1: Overview of Basic Tissues

Epithelial Tissue

Basic tissue composed of layers of cells that cover body surfaces/cavities/tubules/glands

Squamous

Flattened

Cuboidal

Cube-shaped/hexagonal

Columnar

Tall and cylindrical

Transitional

Cells undergo changes in shape

Simple epithelium

Single layer of cells

Stra

Pseudostratified epithelium

Appears to have multiple layers due to varying heights of cells

Simple squamous epithelium

Function of simple squamous epithelium

Allow passage of materials by diffusion and filtration, secretes lubricating substances

Location of simple squamous epithelium

• Kidney corpuscles

• air sacs of lungs

• heart lining

• blood/lymphatic vessels

• lining of central body cavity

Mesothelium

Simple epithelium that lines internal organs (i.e. intestine, lung, and heart)

Endothelium/endocardium

Simple squamous epithelium that covers interior of circulatory vessels and heart chamber

Simple cuboidal epithelium

Single layer of cube-like cells with large, spherical, central nuclei

Function of Simple cuboidal epithelium

Secretion and absorption

Location of Simple cuboidal epithelium

• Kidney tubules

• ducts/secretory portions of small glands

• ovary surface

Simple columnar epithelium

Single layer of tall cells with oval nuclei

Function of Simple columnar epithelium

Absorption, secretion of mucus/enzymes/other substances

Location of Simple columnar epithelium

• Digestive tract

• gallbladder

• excretory ducts of some glands

• small bronchi

• uterine tube/uterus

Stratified squamous epithelium

Thick membrane of several layers of flattened cells and keratin

Function of Stratified squamous epithelium

Protection of underlying tissues against abrasions

Location of Stratified squamous epithelium

Skin epidermis

Stratified cuboidal epithelium

Generally two layers of cuboidal cells

Function of Stratified cuboidal epithelium

Protection and secretion

Location of Stratified cuboidal epithelium

Largest ducts of sweat/mammary/salivary glands

Function of Stratified columnar epithelium

Protection, secretion

Location of Stratified columnar epithelium

(Rare in body) Small amounts in male urethra and large ducts in some glands

Function of Transitional Epithelium

Stretches and permits distension of urinary organ by contained urine

Location of transitional epithelium

Urinary bladder

Pseudostratified columnar epithelium

Single layer of cells with different heights

Function of Pseudostratified columnar epithelium

Secretion/propulsion of mucus

Location of Pseudostratified columnar epithelium

• Trachea

• most of upper respiratory tract

• ducts of large glands

• Microvilli

• cilia

Exocrine Glands

Glands that produce and secrete substances through ducts

Simple gland

Only one unbranched duct

Compound gland

Multiple/branched system of ducts

Merocrine secretion

Uses exocytosis

Examples of merocrine secretion

Sweat, saliva

Apocrine secretion

Cell pinches off apical cytoplasm

Examples of apocrine secretion

Armpits, mammary gland

Holocrine secretion

Entire cell ruptures

Example of holocrine secretion

Sebacous glands → sebum

Serous glands

secrete thin, enzyme-rich fluids

Mucous gland

produce thick, viscous lubricants

Connective tissue

Provides structural support to the body by binding cells and tissues together to form organs

Reticular fibers

Composed of type 3 collagen fibers, proteoglycans, and glycoproteins

Function of reticular fibers

Provides structural framework to support organs (liver, spleen, pancreas, lymph nodes)

Elastic fiber

Resilient nature, important in areas like lungs, aorta, and skin

Types of connective tissue

Loose/areolar, dense regular, dense irregular