Cell Biology Quiz Basics

Epithelial Tissue

• Found in skin, inside the mouth, stomach lining, intestines, lungs, and bladder
• Covers body surfaces and lines organs
• Functions include absorbing, secreting, and protecting
• Types include simple squamous (flat, thin, lining lungs and blood vessels), simple cuboidal (helps filter and release substances; found in kidneys and glands), simple columnar (absorbs nutrients and secretes mucus; in stomach and intestines), pseudostratified columnar (secretes mucus, has cilia for movement; in respiratory tract), stratified squamous (protects from wear and tear, old cells above new; in skin, mouth, vagina, esophagus), stratified cuboidal (secretes substances, more protection than simple cuboidal; in sweat glands), and stratified columnar (protects and secretes, rare; in male urethra and some gland ducts)
• Also includes transitional epithelium (stretches, can change shape; in bladder)
• Cells are tightly packed, forming barriers
• Rapidly regenerates
• Forms glands (sweat and mucus)
• Gland cells cannot be squamous

Cell Junctions

• Tight junctions: Seals cells together to make a watertight seal
• Gap junctions: Small holes/gaps between cells that allow ions to move, facilitating cell communication (in stomach and intestines)
• Desmosomes: Strong connections between cells (like Velcro); in the skin
• Hemidesmosomes: Attach cells to basement membrane

Membranes

• Mucous membranes: Line areas exposed to the outside environment (mouth, nose)
• Serous membranes: Line closed body cavities (around heart and lungs), reducing friction
• Cutaneous membrane: Skin; protects the body
• Synovial membrane: Lines joints, secretes fluid to reduce friction (ex: reduces friction).

Connective Tissue

• Types include loose connective tissue (loosely-packed, few cells; ex: loose areolar, adipose (fat storage)) and dense connective tissue (makes tendons and ligaments strong).
  • Regular Dense CT (lined up collagen, no blood vessels)
  • Irregular Dense CT (very strong, intertwinded, resists many directions)
• Cartilage (firm, flexible, low blood supply): Hyaline cartilage, elastic cartilage, fibrocartilage
• Bone (hard, strong): Compact bone, spongy bone
• Blood (fluid tissue): plasma, red blood cells (erythrocytes), white blood cells (leukocytes), platelets

Muscular Tissue

• Skeletal muscle: Voluntary, moves bones (looks striated, long cells, multiple nuclei)
• Cardiac muscle: Involuntary, pumps blood (looks striated, single nucleus, intercalated discs)
• Smooth muscle: Involuntary, moves food/blood. (no striations, single nucleus)

Nerve Tissue

• Neurons: Send signals; dendrites receive signals; axons send signals; cell body controls neuron
• Glial cells: Support neurons, provide nutrients, remove waste, protect neurons (neuroglia)

Bone Formation

• Intramembranous ossification: Forms flat bones (skull, clavicle) through the development of ossification centers, secretion and calcification of osteoids, forming trabeculae, the development of compact and spongy bone.
• Endochondral ossification: Forms most bones; begins with a hyaline cartilage model, perichondrium turns into periosteum, condrocytes get larger and trigger calcification, blood vessels invade with osteoblasts and osteoclasts, osteoblasts replace cartilage, secondary ossification centers form at the epiphyses, and articular cartilage remains.

Bone Growth

• Interstitial growth (epiphyseal plate): Cartilage cells divide and grow, lengthening the bone until the growth plate closes
• Appositional growth: Osteoblasts add bone tissue to the outer surface of the bone, increasing bone width

Bone Hormones

• Parathyroid hormone (PTH): Pulls calcium from bones into the blood if blood calcium levels are too low
• Calcitonin: Puts calcium in bones when there is too much calcium in blood (when blood calcium levels are too high)
• Vitamin D: Helps the body absorb calcium from food

Fracture Repair

• Hemoatoma formation (early stages)
• Soft callus formation (cartilage + collagen)
• Hard callus formation (temporary bony collar until ossification)
• Bone remodeling.

Summary of Skeletal System

• Skeletal system provides support, protection, movement, mineral storage, and blood cell production
• Bones are made of compact bone (dense outer layer) and spongy bone (porous inner layer).
• Bone cells include osteoblasts (build bone), osteocytes (maintain bone tissue), osteoclasts (resorb bone), and osteogenic cells (stem cells).
• Bone growth is controlled by hormones, genetics, and physical activity, and has stages (interstitial and appositional.)
• Fractures heal in stages.