Weeks 3 &4 - epithelium, connective tissue, and blood

Define epithelium.

A tissue forming continuous sheets of cells that cover body surfaces, line cavities, and form glands.

What separates epithelium from underlying tissue?

Basement membrane.

Explain epithelial cell polarity.

Cells have apical (surface), lateral (neighboring cells), and basal (basement membrane) surfaces.

Name the three criteria for classifying epithelia.

Number of layers, cell shape at the surface, specializations.

What are the three basic epithelial shapes?

Squamous (flat), cuboidal (cube-like), columnar (tall).

What is simple epithelium?

One layer of cells sitting on a basement membrane.

What is stratified epithelium?

Two or more cell layers, only the basal layer contacts the basement membrane.

What is pseudostratified epithelium?

Appears layered but all cells touch basement membrane; nuclei are at various heights.

What is transitional epithelium?

Stratified epithelium with surface cells changing shape in response to stretch, found in urinary tract.

Define glandular epithelium and its functions.

Specialized for secretion, forms exocrine and endocrine glands.

Differentiate exocrine and endocrine glands.

Exocrine secrete via ducts, endocrine release hormones into blood.

What are the modes of exocrine secretion?

Merocrine (pure secretion), apocrine (cytoplasm lost), holocrine (entire cell shed).

What is the function of basement membrane?

Anchors epithelium, barrier for diffusion, provides structural support.

What junction type creates a waterproof seal between cells?

Tight junctions.

What junction type anchors cells together, providing mechanical strength?

Desmosomes.

What junction allows passage of ions and small molecules?

Gap junction.

Name three apical specializations of epithelial cells and their functions.

Cilia (motility), microvilli (absorption), stereocilia (sensory/absorption).

Example locations for simple squamous epithelium.

Alveoli, blood vessels (endothelium), body cavities (mesothelium).

Example function of simple cuboidal epithelium.

Absorption and secretion in kidney tubules, gland ducts.

Where is simple columnar epithelium found?

Digestive tract (intestines), gallbladder.

What is the main function of pseudostratified ciliated columnar epithelium?

Mucus secretion and propulsion in respiratory tract.

Describe the renewal process for epithelial cells.

Continuous replacement by mitosis, especially in basal layers.

What is the main feature of keratinized stratified squamous epithelium?

Surface cells dead, filled with keratin, forms skin barrier.

Give an example of a unicellular gland.

Goblet cells (secretes mucus).

What is an endocrine gland?

Ductless gland, releases hormones into bloodstream.

What are the basic functions of connective tissue?

Structural and metabolic support for other tissues and organs.

What main components constitute connective tissue?

Cells and extracellular matrix (ECM).

What are the two broad parts of ECM?

Ground substance and fibers.

Name three main types of fibers found in connective tissue.

Collagen, elastic, reticular.

What is the primary role of collagen fibers?

Provide tensile strength.

What cells produce ECM in connective tissue proper?

Fibroblasts.

Describe the basic structure of ground substance.

Hydrated gel made of glycosaminoglycans (GAGs), proteoglycans, glycoproteins.

List examples of GAGs.

Hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, heparan sulfate.

What are the main functions of mast cells?

Release histamine (vasodilation) and heparin (anticoagulant), mediate inflammation.

How do embryonic mesenchymal cells relate to adult connective tissue?

Mesenchymal cells are pluripotent stem cells giving rise to all connective tissue cells.

What is the role of adipocytes?

Store fat, insulate and cushion organs.

What is the function of melanocytes in connective tissue?

Produce and store melanin pigment.

Distinguish between loose and dense connective tissue.

Loose—more ground substance and cells; Dense—more fibers, fewer cells.

Where would you find dense regular connective tissue?

Tendons, ligaments.

What is reticular tissue?

Special connective tissue formed of type III collagen, supports organs like liver, spleen.

Describe white and brown adipose tissue.

White—energy storage, insulation; Brown—multiple small fat droplets, lots of mitochondria, generates heat.

What is the matrix of cartilage primarily composed of?

Aggrecans (proteoglycans bound to hyaluronic acid).

What cells are involved in repair and immune defense in connective tissue?

Mesenchymal cells (stem), macrophages, plasma cells, lymphocytes.

What is blood?

Specialized liquid connective tissue, with cellular elements suspended in plasma.

Main functions of blood?

Transport, homeostasis, defense.

What is plasma?

Extracellular matrix of blood, composed mainly of water, proteins, electrolytes, nutrients.

What are the main plasma proteins?

Albumin, globulins (including immunoglobulins), fibrinogen, regulatory proteins.

List the formed elements in blood.

Erythrocytes (RBCs), leukocytes (WBCs), platelets.

Describe erythrocyte morphology.

Biconcave discs in mammals, oval in camels/llamas, nucleated in birds/amphibians.

Which protein is abundant in erythrocytes and what is its role?

Hemoglobin binds and transports oxygen.

What are granulocytes?

Neutrophils, eosinophils, basophils—white blood cells with secretory granules.

What is the main function of neutrophils?

Phagocytosis, acute inflammation.

What do eosinophils do?

Defend against parasites, modulate allergies.

What is unique about basophils?

Contain histamine and heparin granules, rare, mediate allergy.

What are agranulocytes?

Lymphocytes and monocytes; fewer granules.

Distinguish B and T lymphocytes.

B produce antibodies, T responsible for cell-mediated immunity.

What is the role of monocytes in blood?

Become tissue macrophages, phagocytize debris/pathogens.

What are platelets and their function?

Small cell fragments promoting clotting and vascular repair.

What is rouleaux formation?

Stacking of RBCs in a column, seen in blood smears.

What is diapedesis?

Process of leukocytes squeezing through capillary walls to enter tissues.

How do avian blood cells differ from mammalian?

Avian RBCs are nucleated, mammalian are not.

Where are blood cells produced?

Bone marrow (hematopoiesis).

What is the main function of blood in immunity?

Leukocytes travel and act as the body's immune defense.