Histology Basics

What is histology?

The study of tissues.

What is Tissue?

group of cells similar in structure & function.

What are the four basic tissue types?

Epithelial, Connective, Muscle, Nervous.

What is a biopsy?

Examination of tissue removed from a living body to diagnose disease.

What is epithelial tissue?

A sheet of cells that covers body surfaces or cavities.

What are the two forms of epithelial tissue?

Covering/lining (skin, cavities) and glandular (glands).

What are the functions of epithelial tissue?

Protection, absorption, filtration, excretion, secretion, sensory reception.

What are the characteristics of epithelial tissue?

Polarity (top;apical/bottom;basal), specialized contacts, supported by Connective tissue, avascular but innervated;doesnt get blood directly, but is nourished my tissue below, regeneration.

How are epithelial tissues named?

By layers (simple = 1, stratified = 2+) and shape (squamous = flat, cuboidal = cube, columnar = tall).

What is simple squamous epithelium?

Single flat layer; diffusion/filtration; found in lungs, vessels.

What is simple cuboidal epithelium?

Single cube layer; secretion/absorption; found in glands, kidneys.

What is simple columnar epithelium?

Single tall layer; absorption/secretion; may have microvilli, cilia, goblet cells; digestive tract.

What is pseudostratified columnar epithelium?

Appears layered, but single; ciliated; mucus secretion; upper respiratory tract.

What is stratified squamous epithelium?

Multiple flat layers; protection; keratinized (skin), non-keratinized (moist linings), located in areas of high wear and tear.

What is stratified cuboidal/columnar epithelium?

Rare; sweat glands, mammary glands, male urethra.

What is transitional epithelium?

Stretches; bladder, ureters, urethra.

What is a Gland?

One or more cells that makes and secretes an aqueous fluid called secretion.

Sites of product release

Exocrine and Endocrine

What is an exocrine gland?

Ducts, secrete externally (sweat, oil).

What is an endocrine gland?

Ductless, secrete into blood (hormones).

What are the three types of exocrine secretion?

Merocrine (exocytosis – sweat, pancreas), Holocrine (rupture – sebaceous), Apocrine (apex ruptures – armpit, genital).

What is the most abundant & diverse tissue type?

Connective tissue.

What are the functions of connective tissue?

Bind/support, protect, insulate, store energy, transport.

What are the four classes of connective tissue?

CT Proper (loose, dense), cartilage, bone, blood.

What are the characteristics of connective tissue?

Mesenchyme origin, vascularity varies, cells in extracellar maxtrix(ECM)

What are the elements of connective tissue?

Ground substance (gel, fluid, proteoglycans), fibers (collagen, elastic, reticular), cells (blasts make ECM , cytes maintain ECM).

What is areolar connective tissue?

Most common, contains fibroblast that secretes collagen fibers, reservoir for fluid.

What is adipose connective tissue?

Fat storage; white (storage), brown (heat in infants).

What is reticular connective tissue?

Stroma for lymph nodes, spleen, marrow.

What is dense regular connective tissue?

Clean shape, Parallel collagen, tensile strength; tendons/ligaments.

What is dense irregular connective tissue?

Messy shape, Irregular collagen, resists tension; dermis, capsules.

What is dense elastic connective tissue?

Stretch/recoil; arteries, vertebrae ligaments.

What are the properties of cartilage?

Avascular, 80% water, tough/flexible.

What are the three types of cartilage?

Hyaline , Elastic, Fibrocartilage.

What is Hyaline?

most abundant, nose, ribs, joints

What is Elastic( cartilage)?

more elastic fibers, ear, epiglottis

What is Fibrocartilage?

discs, meniscus( designed to cushion)

How does cartilage heal with age?

Poorly, slow healing.

What are the functions of bone?

Support/protect, store fat, make blood cells.

What cells are in bone tissue?

Osteoblasts build, osteocytes maintain.

What is bone’s blood supply like?

Rich blood supply.

What are the components of blood?

Plasma + formed elements (RBCs, WBCs, platelets).

What is the function of blood?

Transport.

What is skeletal muscle?

Voluntary, striated, attached to bone.

What is cardiac muscle?

nvoluntary, striated, branched (heart).

What is smooth muscle?

Involuntary, no striations (GI tract, vessels).

What are neurons?

Cells that transmit impulses.

What are glial cells?

Cells that support, insulate, protect neurons.

Where is nervous tissue found?

Brain, spinal cord, nerves.

What two ways can repair occur?

Regeneration and Fibrosis

What is regeneration?

Restores original tissue.

What is fibrosis?

Scar tissue, loss of function.

Which tissues have good regeneration?

Epithelium, bone, areolar, dense irregular.

Which tissues have moderate regeneration?

Smooth muscle, dense regular.

Which tissues have poor regeneration?

Cardiac muscle, nervous tissue (CNS).

What are the steps of tissue repair?

Hemostasis, Inflammation, Proliferation, and Remodeling

What is Hemostasis?

Blood clotting

What is Inflammation?

Release of inflammatory chemicals.

What is Proliferation?

Growth of new tissue and angiogenesis

What is Remodeling?

collagen reorganization, apoptosis of unecessary cells.

How do tissues function in youth?

Good repair with diet/circulation.

How do tissues change with aging?

Epithelia thin, repair slows, bone/muscle/nervous tissue atrophy, more DNA mutations = higher cancer risk.