Tissues, Membranes, Blood, and the Integumentary System

Comprehensive vocabulary flashcards covering the four primary tissue types, body membranes, blood components and hemostasis, and the integumentary system.

Differentiation

The developmental process occurring soon after conception in which unspecialized cells specialize into distinct cell types structured for specific bodily functions.

Apical Surface

The exposed, unattached free surface or edge possessed by all epithelial tissues that faces the body exterior or the cavity of an internal organ.

Basement Membrane

A structureless material secreted by both epithelial cells and connective tissue cells that binds and anchors the lower basal surface of an epithelium.

Simple Squamous Epithelium

A single layer of flattened, scale-like cells that forms thin membranes lining body cavities, capillary walls, and lung air sacs for rapid diffusion.

Simple Cuboidal Epithelium

A single layer of cube-shaped cells common in glands and their ducts, which forms the walls of kidney tubules and covers the surface of the ovaries.

Simple Columnar Epithelium

A single layer of tall, column-like cells lining the digestive tract; it frequently includes mucus-producing goblet cells and may be ciliated.

Pseudostratified Columnar Epithelium

A single layer of columnar cells resting on a basement membrane that gives a false impression of stratification due to varied cell heights and nuclei positions; typically ciliated and lines respiratory passages and parts of the male reproductive system.

Stratified Squamous Epithelium

A thick epithelial tissue consisting of multiple cell layers whose surface cells are flattened; functions as a protective barrier in areas receiving high friction, such as the skin, mouth, and esophagus.

Transitional Epithelium

A highly modified, stratified epithelium lining organs of the urinary system (such as the bladder) whose cell shapes change and flatten in response to stretching.

Endocrine Glands

Ductless glands that produce regulatory secretions (hormones) and release them directly into surrounding blood vessels or tissues inside the body.

Exocrine Glands

Glands that release their secretions through ducts onto internal or external epithelial body surfaces, such as sweat glands and oil glands.

Extracellular Matrix

The non-living substance surrounding connective tissue cells consisting of ground substance and fibers, allowing connective tissues to withstand stretching, abrasion, and weight.

Osseous Tissue

Bone tissue composed of osteocytes residing in cavities called lacunae, surrounded by a very hard matrix of calcium salts and collagen fibers to protect and support the body.

Hyaline Cartilage

The most widespread cartilage type, composed of chondrocytes embedded in a rubbery collagen-rich matrix; forms the voice box (larynx) and attaches ribs to the breastbone.

Elastic Cartilage

A flexible cartilage type containing chondrocytes, collagen fibers, and numerous elastic fibers within a solid matrix, providing support and elasticity to the external ear.

Fibrocartilage

A highly compressible connective tissue with chondrocytes and a dense collagen fiber matrix that forms cushion-like shock-absorbing discs between the vertebrae of the spinal column.

Dense Connective Tissue

A collagen-packed connective tissue populated by fibroblasts that forms strong cord-like structures, including tendons (attaching muscle to bone) and ligaments (attaching bone to bone).

Areolar Connective Tissue

The most widely distributed connective tissue in the body; a soft, pliable, loose network of fibers and fibroblasts that cushions, wraps, and holds body organs together and in place.

Adipose Tissue

Commonly known as fat; a specialized connective tissue dominated by adipocytes containing large oil droplets with little matrix, functioning in insulation, mechanical protection, and fuel storage.

Reticular Connective Tissue

A delicate network of interwoven reticular fibers and reticular cells that forms the internal supporting framework (stroma) for free white blood cells in lymphoid organs like lymph nodes, the spleen, and bone marrow.

Skeletal Muscle

Voluntary muscle tissue attached to bones or connective tissue featuring long, cylindrical, multinucleated, and striated cells that contract to produce body movements.

Cardiac Muscle

Involuntary striated muscle found exclusively in the heart walls; composed of branching uninucleated cells connected by intercalated discs.

Intercalated Discs

Specialized gap junctions connecting adjacent cardiac muscle cells that allow free ion passage so electrical impulses travel rapidly across the heart to coordinate contractions.

Smooth Muscle

Involuntary, non-striated muscle tissue consisting of spindle-shaped cells with a single central nucleus that line hollow internal organs such as the stomach, uterus, and blood vessels.

Neurons

Specialized nerve cells possessing a central cell body and branching cytoplasmic processes extending up to $3\text{ feet}$ in length, adapted to receive and conduct electrochemical impulses.

Cutaneous Membrane

The skin; an epithelial membrane consisting of keratinizing stratified squamous epithelium firmly attached to a thick layer of dense connective tissue, representing a dry protective boundary.

Mucous Membrane

A wet, mucus-coated epithelial membrane resting on a loose connective tissue lamina propria that lines body cavities opening directly to the exterior, including the respiratory, digestive, urinary, and reproductive tracts.

Serous Membrane

A two-layered membrane composed of simple squamous epithelium resting on areolar connective tissue that lines ventral body cavities closed to the exterior, separated by a thin lubricating serous fluid.

Peritoneum

The specific serous membrane lining the abdominal cavity (parietal peritoneum) and covering the abdominal organs (visceral peritoneum).

Pleura

The serous membrane enclosing the lungs within the thoracic cavity, consisting of an outer parietal layer lining the cavity wall and an inner visceral layer covering the lung surface.

Pericardium

The serous membrane surrounding the heart, consisting of an outer parietal pericardium and an inner visceral pericardium.

Synovial Membrane

A connective tissue membrane without epithelial cells that lines the fibrous capsules surrounding movable joints, producing lubricating synovial fluid.

Formed Elements

The cellular, living components of blood, which include erythrocytes, leukocytes, and platelets suspended in plasma.

Blood Plasma

The non-living liquid extracellular matrix of blood, composed of approximately $90\%$ water and dissolved solutes including nutrients, salts, respiratory gases, hormones, metabolic wastes, and clotting proteins.

Erythrocytes

Red blood cells; anucleate biconcave discs lacking most organelles that function to transport oxygen throughout the bloodstream, outnumbering leukocytes $1000:1$.

Hemoglobin

An iron-bearing globular protein found in erythrocytes that binds reversibly to oxygen; each erythrocyte contains approximately $250\text{ million}$ molecules, with each molecule carrying $4$ oxygen molecules.

Leukocytes

White blood cells; complete nucleated cells containing organelles that defend the body against bacteria, viruses, parasites, and tumor cells.

Diapedesis

The active passage of white blood cells slipping into and out of intact blood vessel walls to reach damaged or infected tissues.

Granulocytes

A subgroup of leukocytes possessing visible cytoplasmic granules when stained, including neutrophils, eosinophils, and basophils.

Agranulocytes

A subgroup of leukocytes that lack visible cytoplasmic granules under staining, comprising lymphocytes and monocytes.

Neutrophils

The most numerous granulocytic leukocytes that function as active, aggressive phagocytes during acute infections.

Eosinophils

Granulocytes equipped with red-staining cytoplasmic granules that respond to allergies and defend against parasitic worms.

Basophils

The rarest granulocytic leukocytes containing dark histamine granules that discharge to initiate inflammation at injury sites.

Lymphocytes

Agranulocytes possessing a large round nucleus and minimal cytoplasm that play a central role in the specific immune response.

Monocytes

The largest circulating agranulocytic white blood cells; they migrate into tissues and transform into macrophages to fight chronic infections.

Platelets

Irregularly shaped, anucleate cell fragments derived from multinucleate megakaryocytes that are essential for normal blood clotting.

Hemostasis

The fast, localized physiological process that stops bleeding when a blood vessel breaks, proceeding in three phases: vascular spasms, platelet plug formation, and coagulation.

Vascular Spasms

The initial phase of hemostasis where vascular smooth muscle contracts in response to injury, local pain receptors, and platelet-released serotonin, causing vasoconstriction to decrease blood loss.

Platelet Plug Formation

The second phase of hemostasis in which platelets adhere to collagen fibers exposed by vessel injury, secrete chemicals attracting more platelets, and aggregate into a mass.

Coagulation

The complex cascade of blood clotting wherein tissue factor, platelet factor 3 ($\text{PF3}$), clotting factors, and calcium ions form prothrombin activator, converting prothrombin to thrombin to assemble an insoluble fibrin mesh.

Fibrin

An insoluble, hair-like protein mesh produced by thrombin cleavage of soluble fibrinogen, which traps red blood cells and platelets to complete a blood clot.

Antigens

Genetically determined proteins located on the external surface of red blood cell plasma membranes that can stimulate immune defenses and agglutinate if recognized as foreign.

ABO Blood Group

A blood grouping system based on the presence or absence of genetically inherited type A and type B antigens on erythrocytes.

Rh Blood Group

A blood classification system determined by the presence ($\text{Rh}^+$) or absence ($\text{Rh}^-$) of one of eight Rh antigens on red blood cell membranes.

Epidermis

The outermost protective layer of skin composed of stratified squamous keratinized epithelium; it is completely avascular.

Dermis

The vascular, deep inner skin layer underlying the epidermis, composed of dense fibrous connective tissue.

Hypodermis

Subcutaneous adipose and connective tissue located deep to the dermis (not part of the skin) that anchors skin to underlying muscle and bone while insulating the body.

Stratum Basale

The deepest epidermal layer bordering the dermis; contains dividing stem cells, melanocytes, and receives nourishment via diffusion from dermal capillaries.

Stratum Spinosum

The epidermal layer directly superficial to the stratum basale whose cells begin flattening and accumulating keratin.

Stratum Granulosum

The intermediate layer of the epidermis where cells become increasingly flat, accumulate dense granules, and begin to die.

Stratum Lucidum

A clear, dead epidermal layer found exclusively in the thick, hairless skin of the palms of the hands and soles of the feet.

Stratum Corneum

The outermost epidermal layer made of $20\text{–}30$ rows of flat, dead, keratin-filled cells that continuously slough off and are renewed every $25\text{–}45\text{ days}$.

Papillary Layer

The upper dermal layer characterized by finger-like dermal papillae projecting into the epidermis, housing capillary loops, pain receptors, and touch receptors.

Reticular Layer

The deeper, thicker layer of the dermis containing dense irregular connective tissue, large blood vessels, sweat glands, sebaceous glands, and deep pressure receptors.

Blister

A fluid-filled pocket that forms when severe burns or friction cause the epidermis and dermis to separate, allowing interstitial fluid to accumulate.

Sebaceous Glands

Cutaneous oil glands that produce antibacterial, lubricating sebum; usually empty into hair follicles and become active at puberty.

Eccrine Sweat Glands

Widespread cutaneous sweat glands that produce a clear, watery secretion discharging directly through skin pores to dissipate excess body heat.

Apocrine Sweat Glands

Specialized sweat glands whose ducts empty into hair follicles; they produce secretions containing fatty acids and proteins that generate body odor when metabolized by bacteria.

Arrector Pili

Small bands of smooth muscle cells connecting hair follicles to the dermis that contract under cold or fright, pulling hairs erect and creating goose bumps.

Hair Shaft

The keratinized portion of a hair extending beyond the surface of the skin, composed of an inner medulla, a surrounding cortex, and an outermost protective cuticle.

Nail Matrix

The thickened proximal portion of the nail bed beneath the cuticle responsible for continuous cellular division and nail growth.

Lunula

The white, crescent-shaped region located at the proximal base of the nail body directly overlying the nail matrix.

Melanin

A dark protective pigment synthesized by melanocytes ranging from yellow to rust to brown and black, which shields keratinocyte DNA against ultraviolet radiation damage.

Melanocytes

Specialized spider-shaped cells located in the stratum basale of the epidermis that synthesize melanin in response to genetic instructions and sun exposure.

Albinism

An inherited genetic condition where a person is born with melanocytes that produce little or no melanin pigment in skin, hair, or eyes.

Carotene

An orange-yellow pigment found in carrots and other orange, deep yellow, or leafy green vegetables that accumulates in the stratum corneum and subcutaneous fat.

Scar Tissue

Dense, collagen-rich fibrous connective tissue that permanently replaces destroyed cutaneous tissue when severe wounds impair normal parenchymal regeneration.