Epithelium

What does hematoxylin bind? Color it produces?Stains more readily with what dyes?

Negatively charged structures like DNA and nuclei; creates blue/purple color; think hemaTOXylin=toxic is negative; stains more readiliy with basic dyes; hema for hematoma which are often blue/purple

What does eosin bind? Color? Stains more readily with what dye?

Positively charged structures like proteins and cytoplasm; think EW sin like sinning is gross which is a positive thought; color is PINK; has affinity for acidic dyes

What does basophilic mean?

Affinity for basic dyes, common in negatively charged structures.

What does eosinophilic mean?

Affinity for acidic dyes, common in positively charged components.

How does electron microscopy work?

It scatters electrons to form high-resolution images with contrast.

What are pros and cons of electron microscopy?

Pros: excellent resolution; Cons: long processing, low labeling specificity.

How does immunohistochemistry differ from H&E?

It uses antibodies(think immune system) to tag specific proteins, requires enzymatic pigment deposition.

What is immunofluorescence?

Technique using antibodies and fluorescent markers to visualize antigens with UV microscopy.

Why is antigen selection important in immunohistology?

Some proteins may be hard to target due to pigmentation or autofluorescence.

What motor proteins move along microtubules? What directions

Kinesins (- to +) and dyneins (+ to -) and cilia/flagella movement).

What motor protein acts on actin filaments?

Myosins; involved in muscle contraction, vesicle transport, and stereocilia development.

What are the eight structural characteristics of epithelial tissues? (JACBARKS)

Junctions, Apical/Basal polarity, Cellular organization, Basement membrane, Avascularity, Regeneration, Keratin expression, Surface Specializations (JACBARKS).

What is apical-basal polarity?

Epithelial cells have distinct top (apical) and bottom (basal) surfaces.

What is the basement membrane?

Thin connective tissue layer beneath epithelial cells providing support and anchorage.

Why is epithelial tissue avascular?

Epithelial cells rely on diffusion from underlying tissues for nutrients.

What is the role of microvilli?

Increase surface area for absorption; contain actin helices.

What is a clinical example of microvilli dysfunction?

Celiac disease: autoimmune damage to brush border reduces absorption.

What is the structure of cilia?

9 microtubule doublets + 2 singlets arrangement; motile.

What condition results from defective cilia?

Kartagener syndrome: immotile cilia → infertility (in men sperm are immotile; in women fallopian tube cilia are disfunctional),URI infections, situs inversus(heart is right side).

What are stereocilia? Where are they found?

Long, branched, non-motile projections that aid fluid absorption or motion sensing. Proximal ductus deferens, epididymis, and sensory cells of the inner ear.

What do desmosomes do?

Provide lateral and basal strength through intermediate filament attachment.

What do tight junctions do?

Limit passage of water and solutes between epithelial cells; claudins+occludins

What do adherens junctions do?

Connect cadherins to actin microfilaments; assist with morphogenesis.

What do gap junctions do?

Enable ion and small molecule transfer between adjacent cells. Found in muscles, neurons and glia

Which junction connects cells to the basement membrane?

Hemidesmosomes.

How are epithelial tissues classified by cell shape?

Squamous (thin+flat), cuboidal (square), columnar (tall and rectangular), transitional (variable).

How are epithelial tissues classified by layers?

Simple (single layer), stratified (multiple layers), pseudostratified (single layer with varying nuclei positions).

Where is simple squamous epithelium found?

Alveoli, blood vessels, lymphatic vessels; allows gas/nutrient exchange.

Where is stratified squamous epithelium found?

Skin, oral cavity, esophagus; protects against abrasion.

Where is simple cuboidal epithelium found?

Kidney tubules, glands; functions in absorption and secretion.

Where is stratified cuboidal epithelium found?

Sweat and mammary DUCTs; adds structural protection.(square DUCTs)

Where is simple columnar epithelium found?

Stomach, intestines, uterine tubes; protects and absorbs. COLUMNAR have little fingers on top like villi

Where is stratified columnar epithelium found?

Pharynx, anus, salivary ducts; provides protection.

Where is pseudostratified columnar epithelium found?

Trachea, bronchi, male reproductive tract; functions in secretion and protection. (not actually stratified, they are flat and use cilia to move things in tight places ex: moving mucus in respiratory tract

Where is transitional epithelium found?

Urinary bladder, ureters; allows stretch and recoil.

What are keratinized epithelia?

Surface cells filled with keratin; found in skin and high-friction zones.

What is the difference between endocrine and exocrine glands?

Endocrine: no ducts, secrete hormones into blood; (inside) vs Exocrine: ducts secrete onto surface.; ex: sweat, salivary,mammary,lacrimal (tears)

What does holocrine secretion involve?

Whole cell disintegration to release contents (e.g., sebaceous glands).

What does apocrine secretion involve?

Apical portion of the cell is pinched off (e.g., mammary glands). The top part.

What does merocrine secretion involve?

Exocytosis of vesicle contents (e.g., sweat glands). “merely secretions”

What are the four types of tissue membranes?

Mucous, serous, cutaneous, synovial.

$$Where are mucous membranes found?

Line external passageways: digestive, respiratory, urinary, reproductive tracts.

What are mucosa layers composed of?

Epithelium + lamina propria (connective tissue).

Where are serous membranes found?

Lining internal cavities: peritoneum(covers abdominal organs), pleura(covers lungs), pericardium(covers heart). Line the real SERiOUS parts of our body that keep us alive (heart, lungs, abdominal organs)

What is the difference between serosa and adventitia?

Serosa: intraperitoneal and free-moving; Adventitia: retroperitoneal and bound.

What is the cutaneous membrane?

The skin; thick, waterproof, and dry barrier.

Where are synovial membranes found?

Line joint cavities; produce lubricating synovial fluid.

What are type A and B synovial cells?

Type A: macrophage-like, remove debris; Type B: produce hyaluronan for lubrication.