Anatomy and Physiology Chapter 4-6

Passive vs. active transport

Passive transport does not require energy and moves high to low concentration. Active transport uses energy; primary active transport can move low to high concentration.

Primary vs. secondary active transport

Primary uses ATP directly. Secondary uses energy stored in an ion gradient.

Endocytosis vs. exocytosis

Endocytosis moves materials into the cell. Exocytosis moves materials out of the cell.

Histology

The division of microscopic anatomy that studies the normal structures of tissues.

Tissue

A group of structurally and functionally related cells and their external environment that together perform common functions.

Tissue level of organization

Cells combine to form tissues; tissues combine to form organs; organs combine to form organ systems.

Levels around the tissue level

Cellular level -> tissue level -> organ level -> organ system level -> organism.

Four major tissue types

Epithelial, connective, muscle, and nervous tissue.

Epithelial tissue - general structure

Tightly packed sheets of cells with very little visible extracellular matrix.

Elastic fibers

Protein fibers that allow tissue to stretch and recoil.

Reticular fibers

Thin branching fibers that form supportive, weblike networks.

Cell junction

A point of contact between adjacent cell membranes that helps maintain contact, strength, or communication.

Tight junction

Seals the space between adjacent cells, making it relatively impermeable to macromolecules.

Desmosome

Anchors neighboring cells together and increases tissue strength against mechanical stress.

Gap junction

Small channels between adjacent cells that allow ions and small substances to pass directly from cell to cell.

Junction comparison

Tight junction = seal; desmosome = anchor; gap junction = communication.

Epithelial classification

classified by number of cell layers and the shape of the cells at the free/apical surface.

Simple squamous epithelium

One layer of flat cells. Function: diffusion and filtration. Locations include lung air sacs and blood vessel lining.

Endothelium

Simple squamous epithelium lining blood vessels and the heart.

Mesothelium

Simple squamous epithelium forming the epithelial portion of serous membranes.

Simple cuboidal epithelium

One layer of cube-shaped cells. Function: secretion and absorption. Locations include kidney tubules and thyroid gland.

Simple columnar epithelium

One layer of tall cells. Nonciliated forms mainly absorb and secrete; common in the digestive tract.

Ciliated simple columnar epithelium

Uses cilia to move fluid or particles across the epithelial surface.

Ciliated pseudostratified columnar epithelium

Often has goblet cells and cilia; secretes and moves mucus. Common in respiratory passages and nasal cavity

Stratified squamous epithelium

Many layers with flattened surface cells; protects against abrasion.

Keratinized stratified squamous epithelium

Dry protective epithelium with dead, keratin-filled surface cells; forms the epidermis.

Exocrine gland

Releases product through a duct to an epithelial surface; effects are usually local.

Endocrine gland

Ductless gland that releases hormones into the blood for action on distant target cells

Unicellular exocrine gland

Single secretory cell; the goblet cell is the classic example.

Multicellular exocrine gland

Many secretory cells plus a duct; examples include sweat, oil, and salivary glands.

Simple exocrine gland

Has an unbranched duct.

Compound exocrine gland

Has a branched duct system.

Tubular secretory portion

Secretory portion is tube-shaped.

Acinar secretory portion

Secretory portion is rounded or saclike.

Merocrine secretion

Product is released by exocytosis; the secretory cell remains intact.

Blast vs. cyte naming

blast usually indicates an immature, matrix-producing cell;

-cyte usually indicates a mature cell that maintains tissue.

Collagen fiber role

Provides high tensile strength and resists pulling forces.

Elastic fiber role

Allows stretch and recoil.

Reticular fiber role

Forms a delicate supportive meshwork.

Two broad connective tissue groups

Connective tissue proper and specialized connective tissue.

Connective tissue proper

Includes loose/areolar, dense connective tissue, reticular tissue, and adipose tissue.

Specialized connective tissues

Cartilage, bone, and blood.

Loose areolar connective tissue

Abundant ground substance with all three fiber types; flexible support beneath epithelia and around structures

Reticular connective tissue

Contains many reticular fibers forming a network that supports cells in spleen and lymph nodes.

Fibrocartilage

Strong cartilage with abundant collagen bundles; found in intervertebral discs and parts of the knee.

Elastic cartilage

Elastic-fiber-rich cartilage; found in the external ear and epiglottis.

Perichondrium

Connective tissue covering around many cartilages; absent around fibrocartilage.

Bone / osseous tissue

Specialized connective tissue with collagen plus mineralized ground substance containing calcium and phosphate

Blood

Fluid connective tissue whose ECM is plasma and whose cells include erythrocytes and leukocytes

Areolar connective tissue - location

Common beneath epithelia, in skin, and around body cavities and hollow organs.

Dense irregular connective tissue - location

Dermis, joint capsules, valves, and other sites exposed to multidirectional stress.

Dense regular collagenous tissue - location

Tendons and many ligaments.

Dense regular elastic tissue - location

Large arteries and selected elastic ligaments/structures that must stretch and recoil.

Skeletal muscle tissue

Long cylindrical, striated, multinucleated fibers; voluntary; usually attached to bones.

Cardiac muscle tissue

Short, branched, striated cells with central nuclei; involuntary; found only in the heart.

Smooth muscle tissue

Spindle-shaped, nonstriated, uninucleate cells; involuntary; found in walls of hollow organs and other structures.

Intercalated disc

Specialized junction between cardiac muscle cells; includes gap junctions and helps cells contract together

Skeletal muscle function

Produces voluntary body movement, posture, and movement of the skeleton.

Cardiac muscle function

Contracts rhythmically to pump blood through the cardiovascular system.

Smooth muscle function

Moves materials through hollow organs and regulates diameter of tubes and passageways

Peristalsis

Wave-like smooth muscle contractions that propel contents through the digestive tract.

Neuroglia / glial cells

Supporting cells of nervous tissue that protect and maintain neurons.

Organ

A body structure made of multiple tissue types that work together to perform specific functions

Tissues working together

An organ's epithelial, connective, muscle, and/or nervous tissues contribute different functions that combine into organ function.

Body membrane

Thin sheet of one or more tissues that covers or lines body parts and may anchor, protect, secrete, or participate in immunity.

Serous membrane

True membrane lining closed body cavities and covering organs; composed of mesothelium plus underlying connective tissue

Serous fluid

Lubricating fluid secreted by serous membranes to reduce friction as organs move

Serous membrane locations

Pleural, pericardial, and peritoneal membranes/cavities.

Synovial membrane

True membrane lining freely movable joint cavities; lacks epithelium and secretes synovial fluid.

Tissues that regenerate well

Epithelial tissues, bone, many connective tissues, blood-forming tissue, and smooth muscle generally regenerate relatively well.

Tissues that often heal by fibrosis

Cartilage, skeletal muscle, cardiac muscle, and much nervous tissue have limited regeneration and commonly heal with fibrosis.

Why repair ability differs

Repair depends on mitotic activity/stem cells, blood supply, severity of injury, and the tissue's structural complexity

Skin structure

The skin itself consists of a superficial epidermis and a deeper dermis.

Hypodermis

Layer beneath the dermis; not technically part of the skin. It contains loose connective and adipose tissue.

Epidermis

Avascular keratinized stratified squamous epithelium forming the superficial skin layer.

Dermis

Vascular connective tissue layer beneath the epidermis; contains vessels, nerves, receptors, hair follicles, and glands

Integumentary system components

Skin plus accessory structures including hair, nails, sweat glands, and sebaceous glands

Stratum granulosum

Keratinocytes flatten and contain granules involved in keratinization and waterproofing.

Stratum lucidum

Clear layer present only in thick skin.

Stratum corneum

Outermost layer of dead, flattened, keratinized cells.

Keratinocyte

Most abundant epidermal cell; produces keratin and forms the protective barrier.

Keratinocyte life cycle

Born in the basale, pushed upward through strata, accumulates keratin, dies, enters the corneum, and is eventually shed.

Why superficial keratinocytes die

They move too far from the blood supply in the dermis to receive adequate nutrients and oxygen.

Melanocyte

Pigment-producing cell in the basal layer; synthesizes melanin and transfers it to keratinocytes.

Dendritic cell

Phagocytic immune cell, especially in the stratum spinosum, that helps protect against pathogens.

Tactile / Merkel cell

Sensory cell in the stratum basale associated with nerve endings and light touch.

Dermal papillae

Projections of papillary dermis into the epidermis that strengthen attachment and increase surface area.

Functions of dermal papillae

Improve epidermal attachment and exchange; some contain capillary loops and sensory receptors.

Dermal ridges

Mounds of papillary dermis arranged into ridges that create overlying epidermal ridges.

Epidermal ridges

Raised surface patterns such as fingerprints created by underlying dermal ridges; increase friction/grip.

Tension / cleavage lines

Lines caused by the predominant orientation of collagen bundles in the reticular dermis.

Melanin

Primary skin pigment, derived from tyrosine, produced by melanocytes

Melanosome

Organelle in melanocytes where melanin is produced and packaged.

Tyrosinase

Enzyme involved in melanin synthesis from tyrosine.

Albinism

Inherited reduction or absence of melanin production despite the presence of melanocytes.

Vitiligo

Loss of melanocytes in patches, producing areas of depigmentation.

Hair / pilus

Filament of dead, keratinized keratinocytes that protects and helps sense the environment.

Hair shaft

Part of the hair extending above the skin surface.

Hair root

Part of the hair located within the skin.

Hair follicle

Epidermal structure extending into the dermis that surrounds and produces hair.