A&PL Key Terms Topic 2

Epithelial tissue

body tissue made of tightly packed cells that cover outer body surfaces

Connective tissue

supports, binds, protects, and gives structure to other tissues and organs in the body

Muscle Tissue

soft, specialized tissue made of long, slender cells called muscle fibers that create movement

Nervous Tissue

Primary tissue in the brain, spinal cord, and nerves that controls and coordinates body functions

lumen

the hollow cavity of a tubular structure

Apical Surface

the exposed surface of the epithelial cell that faces an open space

Basal surface

the side of the cell opposite the apical surface that faces the basement membrane

Basement Membrane

Thin, specialized layer of extracellular matrix, providing support

simple squamous epithelium

single layer of flat, scale-like cells that rest on a basement membrane

simple cuboidal epithelium

single layer of cube-shaped cells on the basement membrane

single columnar epithelium

single layer of column-shaped cells that rest on a basement membrane, specialized for absorption or secretion

goblet cell

specialized column-shaped cell whose primary function is to synthesize/secrete mucus

microvilli

tiny projections of the cell plasma membrane to increase surface area for absorption and secretion

pseudostratified columnar epithelium

a single layer of irregularly shaped columnar cells, nuclei sit at different heights

cilia

hair-like organelle that projects from the surface of eukaryotic cells to move fluids or provide sensory functions

stratified squamous epithelium

multi-layered tissue made of flat, thin cells that protect the body from wear, tear, and water loss

keratinized

filled with a tough, fibrous protein (keratin) that makes cells hard, dry, and waterproof

non-keratinized

does not contain keratin on its surface

stratified columnar epithelium

body tissue made of multiple cell layers with tall, column-shaped cells on the outer surface

transitional epithelium

a specialized type of stratified tissue that changes shape as the underlying organs stretch and relax

Endocrine gland

a ductless organ that secretes chemical messengers (hormones) into the bloodstream

exocrine gland

a type of organ or cell that releases substances through a duct onto an epithelial surface

merocrine

a type of exocrine secretion where cells pack their secretions into vesicles and push them out through the cell membrane

apocrine

a type of exocrine gland that secretes oily, protein-rich fluids into the hair follicles instead of the skin surface

matrix

the non-living material that surrounds, separates, and supports cells within a tissue

fibers

an elongated structural cell filament that forms key components of muscle, nerve, and connective tissue

elastin fibers

connective tissue structures made of the protein elastin that allow tissues to stretch and snap back into place

collagen fibers

protein ropes made of collagen that provide strength to the body’s connective tissues

holocrine

a mode of secretion where the secretory cell ruptures and disintegrates, releasing its products and cell debris

reticular fibers

protein fibers that branch into a supportive, mesh-like network inside soft and cellular organs

ground subtance

a clear fluid that fills the spaces between cells and protein fibers inside kenhub connective tissues

fibroblasts

permanent resident cells in connective tissue, responsible for creating and maintaining the structural framework of organs and bodiy structures

mesenchyme

unspecialized type of embryonic tissue made of mobile cells floating in a jelly-like fluid matrix

Loose connective tissue

soft type of connective tisue characterized by a sparse arrangement of protein fibers and abundant ground substance

areolar connective tissue

type of LCT that acts as the body’s flexible packing material, supporting organs and allowing free movement

adipose connective tissue

specialized type of LCT composed of fat-storing cells called adipocytes

reticular connective tissue

type of LCT made of thin type III collagen fibers that support free blood and immune cells

dense connective tissue

fibrous body tissue packed tightly with collagen fibers that provides structural support, strength, and protection to organs, bones, and muscles

dense regular connective tissue

type of DCT made of tightly packed, parallel bundles of type I collagen fibers that provide high tensile strength in one direction

dense irregular connective tissue

tightly packed, randomly interwoven collagen fibers that provide strength against pulling forces from multiple directions

elastic connective tissue

specialized type of DCT packed with a high proportion of stretchy elastic fibers that allow organs and internal structures to stretch and recoil

blood

a specialized fluid connective tissue that circulates through the heart, arteries, veins, and capillaries

plasma

the pale-yellow, liquid portion of blood that makes up ~55% of total blood volume and suspends the blood cells

lymph

a clear fluid derived from interstitial fluid that circulates through the lymphatic system to support immune defense and fluid balance

cartilage

a type of specialized connective tissue that cushions joints, supports flexible body parts, and connects structures together

chondrocytes

the only specialized cells found in healthy cartilage responsible for producing and maintaining the extracellular matrix

lacunae

small cavities in the hard matrix of bone or cartilage that house living cells

perichardrium

a layer of dense irregular connective tissue that surrounds most types of cartilage

hyaline cartilage

connective tissues in the human body, characterized by a smooth, translucent appearence and a resilient extracelluar matrix

elastic cartilage

specialized type of connective tissue packed with elastin fibers that allows body structures to withstand repeated bending

fibrocartilage

the toughest type of cartilage in the human body

bone

a rigid, living organ made of specialized connective tissue that forms the skeletal framework

osteocytes

mature bone cells embedded inside the hardened mineralized bone matrix that make up 90-95% of all cells in adult bone tissue

lacunae (bone)

cavities embedded within the hard, calcified bone matrix

Canaliculi

tiny canals in the body that connect cells to nutriend supplies and allow fluids or secretions to flow

periosteum

dense, fiberous membrane that covers the outer surface of all bones except joints

trabecular bone

a porous, osseous tissue found inside the interior of bones

cortical bone

the dense outer layer of the skeleton that forms the supportive shell of all bones

haversian system (osteon)

the fundamental functional and structural unit of cortical bone

haversian (central) canal

tubular channel located in the center of and osteon within compact bone

volkmann’s (perforating) canal

channels in compact bone that transmit blood vessels and nerves from the outer layer (periosteum) into the interior to communicate with central Haversian canals

epidermis

the outermost layer of skin

dermis

thick middle layer of skin

hypodermis

the deepest layer of skin

keratinocytes

the primary specialized epithelial cells of the epidermis

melanocyte

pigment-producing cells in the skin

stratum basale

the deepest basal layer of the epidermis, directly above the dermis

stratum spinosum

thick middle layer of the epidermis, providing flexibility and mechanical strength

stratum granulosum

thin, intermediate layer of the epidermis consisting of 1 to 5 rows of keratinocytes as protective skin cells

stratum lucidum

a thin, translucent layer of dead skin cells found exclusively in the thick skin of the palms and soles

stratum corneum

outermost sublayer of the epidermis, functioning as the primary physical and chemical barrier

papillary layer

superficial layer of the dermis that sits directly beneath the epidermis

dermal papilla

small elevation of loose connective tissue at the base of a hair follicle or projecting upward into the epidermis

meissner’s corpuscle

a specialized encapsulated mechanoreceptor in the skin that detects light touch or low frequency vibration

reticular layer

thick bottom layer of the dermis that lies between the superficial papillary layer and the subcutaneous hypodermis

pacinian corpuscle

a sensory nerve ending that acts as a mechanoreceptor, converting deep pressure and high-frequency vibration into electrical nerve signals

cleavage lines of the skin

topographical maps on the skin that show the natural alignment of collagen fiber bundles in the reticular layer of the dermis

sebaceous gland

a microscopic exocrine gland in the skin that secretes an oily, waxy substance called sebum

sudoriferous gland

tubular exocrine structures located in the skin that produce and secrete sweat

merocrine gland

an exocrine gland that releases its products via exocytosis without damage to the parent cell

apocrine gland

an exocrine gland in the skin that secretes a thick lipid and protein fluid into hair follicles instead of the skin surface

subcutaneous

the deepest layer of the inegumentary system, situated directly beneath the dermis and above the deep muscle fascia

hair follicle

a specialized appendage embedded in the dermis that anchors, nourishes, and produces a hair strand

arrector pili muscle

tiny bundle of smooth muscle fibers in the skin that connects hair follicles to the papillary layer of the dermis, pulling hairs upright when it contracts

nail body

hard outer portion of the nail that sitss securely on top of the end of the finger/toe

free edge

the outermost, distal tip of the nail plate that extends past the fingertip or toe

nail bed

the specialized layer of living epidermal tissue directly beneath the nail plate

cuticle (eponychium)

the thickened layer of living epidermal tissue located at the base of the finger/toenail

melanin

natural polymer derived from tyrosine that provides pigmentation to the skin, hair, and eyes

malignant melanoma

a type of cancer that starts in the melanocytes

ABCDE rule

a rule for identifying warning signs of melanoma, a- asymmetry, b- border, c-color, d-diameter, e-evolving