histology lecture

What is histology?

The study of normal structures of tissues.

What is a tissue?

A population of cells related in structure and function, with surrounding ECM.

What are the 4 primary tissue types?

Epithelial, connective, muscle, and nervous tissues.

What is the main function of epithelial tissue?

Covers and lines body surfaces and cavities; also forms glands.

What is the main feature of connective tissue?

A prominent extracellular matrix with cells scattered throughout.

What is the main function of muscle tissue?

Contraction.

What do neurons do?

Generate, send, and receive messages.

What do neuroglia do?

Support the activity of neurons.

What is extracellular matrix (ECM)?

Material in a liquid, gel, or solid that surrounds cells.

What is the function extracellular matrix (ECM)?

Provides tissue with strength, Directs cells to proper positions, Regulates development, mitotic activity, and survival of cells

What are the 2 main components of ECM?

Ground substance and protein fibers.

What does ground substance contain?

Water, nutrients, ions, and macromolecules.

What does ground substance main components?

water, nutrients, ions, and macromolecules

What are the components of extracellular matrix macromolecules

Glycosaminoglycans, Proteoglycans, Cell-adhesion molecules (CAMs)

Glycosaminoglycans example

ex. chondroitin sulfate (cartilage) and hyaluronic acid

Proteoglycans

GAGs bound to a protein core

Cell-adhesion molecules (CAMs)

• made up of different types of glycoproteins

• bind surface protein

• maintain the architecture of the tissue

What are the components of protein fibers

• Collagen fibers

• Elastic fibers

• Reticular fibers

What are collagen fibers resistant to?

Tension and pressure.

What is the function of elastic fibers?

They exhibit elasticity.

What is the function of reticular fibers?

Form a weblike scaffold that supports cells and ground substance.

What causes Ehlers-Danlos syndrome?

Abnormal collagen fibers.

What causes Marfan syndrome?

Abnormal elastic fibers.

What are the main functions of epithelial tissue?

Protection, immune defense, secretion, transport, and sensation.

Protection

shield underlying tissues from mechanical and thermal injury; undergoes mitosis rapidly and frequently

Immune defenses

form physical barriers; contain cells of immune system

Secretion

such as sweat, hormones and oils

Transport into other tissues

form selectively permeable membranes

Sensation

detects changes in internal and external environments

Are epithelial tissues vascular or avascular?

Avascular.

How are epithelia classified by layers?

Simple = one layer; stratified = 2+ layers; pseudostratified looks layered but is one layer.

What are the 3 epithelial cell shapes?

Squamous = flat

cuboidal = short

columnar = tall/elongated

What is simple squamous epithelium adapted for?

Rapid diffusion of substances.

Where is simple squamous epithelium found?

Lung air sacs, parts of kidney, and blood vessel walls.

Where is simple cuboidal epithelium found?

Renal tubules, respiratory passages, gland ducts, and thyroid.

Simple columnar epithelium

single layer of rectangular-shaped cells; often has microvilli; or cilia

What do microvilli do?

Increase surface area for absorption.

What do cilia do?

Propel substances through hollow organs.

What is pseudostratified ciliated columnar epithelium?

One cell layer that appears layered because nuclei are at different heights.

Where is pseudostratified ciliated columnar epithelium found?

Segments of the respiratory tract and nasal cavity.

What is keratinized stratified squamous epithelium?

Outer skin layers with dead, nucleus-free cells filled with keratin.

Where is nonkeratinized stratified squamous epithelium found?

Wet mucous membranes such as mouth, throat, esophagus, anus, and vagina.

Where is stratified cuboidal epithelium found

lines ducts of sweat glands

Where is Stratified columnar epithelium found

found in male urethra, cornea of eye, ducts of salivary glands

Where is transitional epithelium found?

Only in the urinary system.

What is special about transitional epithelium?

Apical cells flatten, allowing urinary tissues to stretch.

Glandular Epithelia

specialized cells that produce secretions; Products are released by two mechanisms:
• Endocrine
• Exocrine

What is an endocrine gland?

A ductless gland that releases hormones directly into the bloodstream.

Where is endocrine gland found?

thyroid, pituitary, ovary

What is an exocrine gland?

A gland with ducts whose secretions have local effects.

where is exocrine glands unicellular found?

digestive & respiratory tracts

what is exocrine glands unicellular function?

protects underlying epithelia(goblet cells → mucus)

Where is exocrine gland found?

sweat glands, salivary glands

What is merocrine secretion?

A fluid product released in vesicles.

What is holocrine secretion?

The entire cells are released.

Which gland uses holocrine secretion?

Sebaceous gland.

What are the functions of connective tissue?

Connect/bind, support, protect, and transport.

What are the functions of specialized connective tissue?

Cartilage, Bone, Blood

Connect and bind for connective tissues functions

anchor tissue layers in organs and link organs together

Support for connective tissues functions

bone and cartilage support weight of the body

Protection for connective tissues functions

• bone tissue protects certain internal organs

• cartilage and fat provide shock absorption

• components of immune system found throughout CT

Transport for connective tissues functions

blood main transport medium in body

Characteristics of CT:

Cells, ECM, and usually vascular

What are fibroblasts?

Cells that produce connective tissue fibers.

What do mast cells produce?

Histamine, which causes inflammation.

What do phagocytes do?

Ingest foreign invaders.

What is loose connective tissue (areolar)?

Mostly ground substance plus fibers, fibroblasts, and occasional adipocytes.

Where is areolar tissue(loose CT) found?

Beneath skin epithelium, body-cavity membranes, and hollow-organ walls.

What is dense irregular connective tissue?

Mostly disorganized collagen bundles.

Where is dense irregular connective tissue found?

Dermis and around organs and joints.

What is dense regular connective tissue?

Connective tissue with parallel collagen bundles.

Where is dense regular connective tissue found?

Tendons and ligaments.

What is dense regular elastic connective tissue?

Mostly parallel elastic fibers with some collagen fibers.

Where is dense regular elastic connective tissue found?

Walls of organs that need to stretch, such as large blood vessels.

What is reticular tissue?

A fine network that supports vessels, lymph nodes, spleen, liver, and bone marrow.

What are the functions of adipose tissue?

Fat storage, insulation, shock absorption, and protection.

What are adipocytes?

Fat-storing cells.

What is hypertrophic adipose tissue?

Adipocytes increase in size while their number stays unchanged.

What is hypercellular adipose tissue?

The number of adipocytes increases.

What are the 3 specialized connective tissues?

Cartilage, bone, and blood.

What does cartilage do?

Provides support and is found in joints, ear, nose, and parts of the respiratory tract.

What does Bone tissue do?

supports & protects; muscle attachments; stores calcium, and bone marrow

What does Blood tissue do?

liquid ECM called plasma; consists of mostly water, dissolved solutes, and proteins

What are chondroblasts?

Immature cartilage cells that divide by mitosis and produce ECM.

What are chondrocytes?

Cartilage cells located in lacunae.

Is cartilage vascular?

Mostly avascular.

What are the 3 types of cartilage?

Hyaline, fibrocartilage, and elastic cartilage.

What is the most abundant type of cartilage?

Hyaline cartilage.

Where is hyaline cartilage found?

Ends of long bones, trachea, nose, and most of the fetal skeleton.

What is fibrocartilage known for?

Great tensile strength.

Where is fibrocartilage found?

Intervertebral discs, knee menisci, and symphysis pubis.

What is elastic cartilage known for?

Flexibility.

Where is elastic cartilage found?

External ear, auditory tube, and epiglottis.

What does bone tissue do?

Supports and protects, provides muscle attachments, stores calcium, and contains marrow.

What are the main bone cells?

Osteoblasts, osteocytes, and osteoclasts.

What is the extracellular matrix of blood?

Plasma.

What do erythrocytes do?(red blood cells)

Transport oxygen.

What do leukocytes do?(white blood cells)

Function in immunity.

What do thrombocytes do? (platelets)

Play a major role in blood clotting.

What are the 3 types of muscle tissue?

Skeletal, cardiac, and smooth.