Tissues: Epithelial, Connective, and Nervous Tissues

Vocabulary practice flashcards covering the classification, structures, functions, and locations of epithelial, connective, and nervous tissues.

Epithelial tissue

A primary tissue type that forms boundaries between inside and outside environments (such as the skin) and functions in protection, absorption, filtration, excretion, secretion, and sensory reception.

Apical surface

The upper, free surface of an epithelial tissue that borders open space and may possess cellular specializations such as microvilli or cilia.

Basal surface

The lower surface of an epithelial tissue that attaches to and sits next to underlying connective tissue.

Basement membrane

An extracellular structure located between epithelial tissue and underlying connective tissue, composed of the basal lamina and the reticular lamina.

Basal lamina

The superficial layer of the basement membrane positioned directly beneath the basal surface of the epithelium.

Reticular lamina

The deeper layer of the basement membrane that lies adjacent to the underlying connective tissue.

Simple epithelium

An epithelial tissue consisting of a single layer of cells, typically functioning in moving substances across the cell via diffusion, secretion, or absorption.

Stratified epithelium

An epithelial tissue consisting of two or more layers of cells, functioning primarily in protection against abrasion.

Squamous cells

Epithelial cells characterized by a flattened shape and disc-shaped central nuclei.

Cuboidal cells

Boxlike epithelial cells characterized by large, spherical central nuclei.

Columnar cells

Tall, column-shaped epithelial cells characterized by round to oval nuclei.

Simple squamous epithelium

A single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; allows materials to pass by diffusion and filtration where protection is not important, and secretes lubricating substances in serosae; found in kidney glomeruli, lung air sacs, serosae, and the lining of the heart, blood vessels, and lymphatic vessels.

Simple cuboidal epithelium

A single layer of cubelike cells with large, spherical central nuclei; functions in secretion and absorption; located in kidney tubules, ducts and secretory portions of small glands, and the ovary surface.

Simple columnar epithelium

A single layer of tall cells with round to oval nuclei, often bearing microvilli or cilia and sometimes goblet cells; functions in absorption, secretion of mucus and enzymes, or propulsion via ciliary action; nonciliated form lines most of the digestive tract, gallbladder, and excretory ducts of some glands; ciliated form lines small bronchi, uterine tubes, and regions of the uterus.

Pseudostratified columnar epithelium

A single layer of cells of differing heights with nuclei at different levels where some cells do not reach the free surface; secretes substances (particularly mucus) and propels mucus by ciliary action; ciliated type lines the trachea and upper respiratory tract; nonciliated type lines male sperm-carrying ducts and large gland ducts.

Stratified squamous epithelium

A thick epithelium composed of several cell layers with metabolically active, mitotically dividing basal cells and flattened surface cells; protects underlying tissues in areas subjected to abrasion; nonkeratinized form lines the esophagus, mouth, and vagina; keratinized form forms the dry epidermis of the skin.

Transitional epithelium

A stratified epithelium with cuboidal or columnar basal cells and dome-shaped or squamouslike surface cells depending on stretch; stretches readily to permit distension of urinary organs; lines the ureters, bladder, and part of the urethra.

Exocrine glands

Glands that retain connecting cells during development to form a duct that transports secretions to the epithelial surface.

Endocrine glands

Ductless glands that lose their connecting cells during development, secreting hormones directly into interstitial fluid to enter the blood.

Goblet cell

A mucus-secreting unicellular exocrine gland found in epithelial layers, containing secretory vesicles filled with mucin, a Golgi apparatus, rough endoplasmic reticulum, a nucleus, and apical microvilli.

Primary tissue classes

The four fundamental tissue classes in the human body: epithelial, connective, muscle, and nervous tissue.

Connective tissue

The most abundant and diverse primary tissue class in the body, composed of cells, ground substance, and fibers; functions in support, protection, insulation, storing fuel, and transporting substances.

Extracellular matrix

The non-cellular component of connective tissue surrounding living cells, consisting of ground substance and protein fibers.

Ground substance

The unstructured gel-like or calcified material that fills the space between cells and contains the fibers within connective tissue.

Collagen fibers

Strong, thick fibers found within connective tissue that provide high tensile strength and resist pulling forces.

Elastic fibers

Connective tissue fibers composed of elastin that allow tissues to stretch and recoil passively.

Reticular fibers

Fine, dark-staining connective tissue fibers that branch extensively to form delicate supporting networks or stromata in soft organs.

Areolar connective tissue

A model loose connective tissue proper with a gel-like matrix and all three fiber types, containing fibroblasts, macrophages, mast cells, and white blood cells; wraps and cushions organs, conveys fluid, and participates in inflammation; located under epithelia (e.g., lamina propria) and around capillaries.

Adipose tissue

A loose connective tissue proper containing closely packed adipocytes with sparse matrix and peripherally displaced nuclei due to large fat droplets; stores reserve food fuel, insulates against heat loss, and supports/protects organs; found in subcutaneous tissue, around kidneys and eyeballs, within the abdomen, and in breasts.

Reticular connective tissue

A loose connective tissue proper consisting of a loose network of reticular fibers in gel-like ground substance with reticular cells; forms a soft internal skeleton (stroma) supporting white blood cells, mast cells, and macrophages in lymphoid organs (lymph nodes, bone marrow, and spleen).

Dense regular connective tissue

A dense connective tissue proper composed primarily of parallel collagen fibers, few elastic fibers, and fibroblasts; attaches muscle to bone/muscle or bone to bone, withstanding tensile stress applied in one direction; located in tendons, most ligaments, and aponeuroses.

Dense irregular connective tissue

A dense connective tissue proper containing primarily irregularly arranged collagen fibers, some elastic fibers, and fibroblasts; withstands tension exerted in many directions to provide structural strength; found in fibrous capsules of organs and joints, dermis of the skin, and submucosa of the digestive tract.

Elastic connective tissue

A dense regular connective tissue proper containing a high proportion of elastic fibers; allows tissue recoil after stretching, maintains pulsatile blood flow, and aids lung recoil; located in large artery walls, certain vertebral ligaments, and bronchial tube walls.

Hyaline cartilage

An avascular cartilage featuring an amorphous, firm matrix with an imperceptible network of collagen fibers and chondrocytes in lacunae; cushions, reinforces, and resists compressive stress; found in embryonic skeleton, ends of long bones in joint cavities, costal cartilages, nose, trachea, and larynx.

Elastic cartilage

A type of cartilage similar to hyaline cartilage but containing a higher proportion of elastic fibers in its matrix; maintains structural shape while permitting great flexibility; found supporting the external ear (pinna) and epiglottis.

Fibrocartilage

Cartilage with a matrix less firm than hyaline cartilage where thick collagen fibers predominate, housing chondrocytes in lacunae; absorbs compressive shock with high tensile strength; located in intervertebral discs, the pubic symphysis, and discs of the knee joint.

Bone tissue

A well-vascularized connective tissue containing osteocytes in lacunae within a hard matrix calcified with inorganic salts and collagen fibers; supports, protects, provides levers for muscles, stores minerals and fat, and houses marrow for hematopoiesis; subdivided into compact and spongy bone.

Blood

A fluid connective tissue consisting of red blood cells (erythrocytes), white blood cells (leukocytes), and platelets suspended in a non-fibrous fluid matrix called plasma; transports respiratory gases ($\text{O}_2$, $\text{CO}_2$), nutrients, wastes, and hormones within blood vessels.

Nervous tissue

Tissue composed of branching neurons and nonexcitable supporting cells; transmits electrical signals from sensory receptors to effectors (muscles and glands); found in the brain, spinal cord, and nerves.