A/P Units 5-9

A/P Units 5-9 TRASHY

Histology

The study of tissues and how they are arranged into organs.

Tissue

A group of similar cells and cell products that arise from the same region of the embryo and work together to perform a specific role.

Four primary tissue types

Epithelial, connective, nervous, and muscular tissue.

Matrix (extracellular)

The substance composed of fibrous proteins and a clear gel (ground substance, tissue fluid, ECF, or interstitial fluid) surrounding cells.

Primary germ layers

The first three strata of organized tissues in human development: ectoderm, mesoderm, and endoderm.

Ectoderm

The outer primary germ layer that gives rise to the epidermis and nervous system.

Endoderm

The inner primary germ layer that gives rise to mucous membranes of the digestive/respiratory tracts and digestive glands.

Mesoderm

The middle primary germ layer that turns into mesenchyme, giving rise to muscle, bone, and blood.

Longitudinal section (l.s.)

A tissue cut along its long axis.

Cross section (c.s. / x.s.)

A tissue cut perpendicular to its long axis; also called a transverse section (t.s.).

Oblique section

A tissue cut at an angle.

Smear

A tissue preparation where liquid or soft tissue is rubbed or spread across a slide.

Spread

A tissue preparation where membranes and webby tissues are laid out flat on a slide.

Epithelial tissue

A flat sheet of closely adhering cells, one or more cells thick, with the upper surface usually exposed to the environment or an internal space.

Basement membrane

The layer that anchors an epithelium to the underlying connective tissue.

Simple epithelium

An epithelium in which every single cell touches the basement membrane.

Stratified epithelium

An epithelium in which some cells rest on top of others and do not contact the basement membrane.

Simple squamous epithelium

A single layer of thin, scaly epithelial cells.

Simple cuboidal epithelium

A single layer of squarish, round epithelial cells.

Simple columnar epithelium

A single layer of tall, narrow epithelial cells.

Pseudostratified columnar epithelium

An epithelium that looks layered, but all cells actually reach the basement membrane while shorter cells do not reach the free surface.

Goblet cells

Wineglass-shaped cells found in simple columnar and pseudostratified columnar epithelia that secrete protective mucus.

Stratified squamous epithelium

The most widespread epithelium in the body, consisting of 2 to 20 or more layers where the surface cells are flat and scaly.

Exfoliation (desquamation)

The process where dead surface epithelial cells flake off and separate from the tissue.

Transitional epithelium

A specialized stratified epithelium designed to stretch, erroneously named for representing a "transition" stage.

Integument

Another name for the skin, which is the largest organ of the body.

Integumentary system

The body system composed of the skin and its accessory organs such as hair, nails, and glands.

Dermatology

The medical study of the integumentary system.

Epidermis

The outer, keratinized stratified squamous epithelial layer of the skin that lacks blood vessels.

Dermis

The deeper, connective tissue layer beneath the epidermis of the skin.

Hypodermis

The subcutaneous tissue layer underlying the dermis (not considered a true part of the skin).

Thick skin

Skin covering the palms and soles that contains sweat glands but lacks hair follicles and sebaceous glands.

Thin skin

Skin covering most of the body that contains hair follicles, sebaceous glands, and sweat glands.

Acid mantle

The slightly acidic surface film of the skin (pH 4–6) that limits bacterial growth.

Skin thermoregulation

The process where cutaneous thermoreceptors signal the brain to cause vasoconstriction (to conserve heat) or vasodilation (to shed heat).

Stem cells (skin)

Undifferentiated cells in the stratum basale that divide to give rise to keratinocytes.

Keratinocytes

The majority of epidermal cells, responsible for synthesizing the structural protein keratin.

Melanocytes

Cells in the stratum basale that synthesize the pigment melanin to shield keratinocyte DNA from UV radiation.

Tactile cells

Specialized receptor cells in the stratum basale associated with a dermal nerve fiber for the sense of touch.

Dendritic cells

Immune macropage-like cells found in the stratum spinosum and granulosum that stand guard against foreign pathogens.

Stratum basale

The innermost layer of the epidermis, consisting of a single layer of stem cells and keratinocytes resting on the basement membrane.

Stratum spinosum

Several layers of keratinocytes that appear spiny when fixed due to intact desmosomes holding shrinking cells together.

Osteology

The study of bone tissue and the skeletal system.

Osseous tissue

A connective tissue in which the extracellular matrix is hardened by mineral deposition (mineralization or calcification).

Flat bones

Thin, curved bone plates that enclose/protect soft organs and provide broad surfaces for muscles (e.g., cranial bones, ribs, sternum).

Long bones

Bones that are significantly longer than they are wide, serving as rigid levers for body movement (e.g., humerus, femur, phalanges).

Short bones

Bones nearly equal in length and width that produce limited gliding motion (e.g., carpals and tarsals).

Irregular bones

Bones with complex shapes that do not fit other categories (e.g., vertebrae, middle-ear ossicles).

Compact bone

The dense, white outer shell of osseous tissue that makes up three-quarters of the skeleton's weight.

Medullary cavity

The central space enclosed by the cylinder of compact bone within a long bone shaft; contains bone marrow.

Spongy bone

Cancellous bone tissue found at the ends of long bones and middle of flat bones, always enclosed by compact bone.

Diaphysis

The elongated shaft of a long bone that provides leverage during movement.

Epiphysis

The expanded head at each end of a long bone, enlarged to strengthen joints and provide surface area for tendon/ligament attachment.

Articular cartilage

A layer of hyaline cartilage covering joint surfaces where bones meet, enabling smooth movement.

Nutrient foramina

Minute holes through which blood vessels penetrate into a bone.

Periosteum

The external sheath covering a bone, featuring an outer fibrous collagen layer and an inner osteogenic cell layer.

Perforating fibers

Collagen fibers of the periosteum's outer layer that penetrate deep into the bone matrix.

Endosteum

A thin layer of reticular connective tissue lining the internal marrow cavity and covering spongy bone surfaces.

Epiphyseal plate

A layer of hyaline cartilage separating marrow spaces of the diaphysis and epiphysis in children; acts as the growth plate.

Axial skeleton

The central supporting axis of the body, including the skull, auditory ossicles, hyoid bone, vertebral column, and thoracic cage.

Appendicular skeleton

The bones of the upper limbs, pectoral girdle, lower limbs, and pelvic girdle.

Sesamoid bones

Bones that form within certain tendons in response to mechanical strain (e.g., the patella).

Sutural (Wormian) bones

Extra, unnumbered bones that can form within the sutures of the skull.

Sutures (skull)

Immovable joints that connect most of the 22 bones of the skull.

Cranial cavity

The largest cavity of the skull, which encloses and protects the brain.

Paranasal sinuses

Air-filled, mucous-membrane-lined cavities within the skull bones (frontal, sphenoid, ethmoid, maxillary) connected to the nasal cavity.

Foramen

A conspicuous hole or opening in bone that allows the passage of nerves and blood vessels.

Cranium

The rigid structure composed of 8 bones that protects the brain and associated sensory organs.

Meninges

The three membranes separating the brain from cranial bones, the thickest/toughest of which is the dura mater.

Foramen magnum

The large opening at the base of the cranium where the spinal cord enters to meet the brain stem.

Calvaria

The skullcap forming the roof and walls of the cranium.

Anterior cranial fossa

The crescent-shaped depression in the cranial base accommodating the frontal lobes of the brain.

Middle cranial fossa

The bilateral depression in the cranial base accommodating the temporal lobes of the brain.

Posterior cranial fossa

The deepest depression in the cranial base housing the cerebellum.

Frontal bone

The bone extending from the forehead back to the coronal suture, forming the anterior roof and wall of the cranium.

Diploe

The internal layer of spongy bone located in the middle of flat bones, visible along cut edges of the skull.

Parietal bones

Right and left bones forming most of the cranial roof and upper lateral walls.

Sagittal suture

The cranial joint located between the two parietal bones.

Coronal suture

The cranial joint separating the frontal bone from the parietal bones.

Lambdoid suture

The cranial joint at the posterior margin separating the parietal bones from the occipital bone.

Squamous suture

The cranial joint at the lateral margin separating the parietal bone from the temporal bone.

Temporal bones

Right and left bones forming much of the lower wall and floor of the cranial cavity, situated just around the ear.

Zygomatic process

A prominent feature of the squamous temporal bone that forms part of the cheekbone arch.

Mandibular fossa

The depression on the temporal bone where the mandible articulates with the cranium.

External acoustic meatus

The ear canal opening bordered by the tympanic part of the temporal bone.

Styloid process

A stylus-like downward projection of the temporal bone providing attachment for tongue, pharynx, and hyoid muscles.

Mastoid process

A prominent lump behind the ear filled with small air sinuses subject to infection.

Petrous part

A mountain-range-like region of the temporal bone in the cranial floor housing the middle- and inner-ear cavities.

Internal acoustic meatus

An opening on the petrous temporal bone allowing passage of the vestibulocochlear nerve for hearing and balance.

Occipital bone

The bone forming the rear of the skull (occiput) and much of its base.

Joint (articulation)

Any point where two bones meet, regardless of whether the bones are movable at that interface.

Arthrology

The science of joint structure, function, and dysfunction.

Kinesiology

The study of musculoskeletal movement, a branch of biomechanics.

Bony joint (synostosis)

An immovable joint formed when the gap between two bones ossifies (e.g., fusion of infant frontal bones).

Fibrous joint (synarthrosis)

A joint where adjacent bones are tightly bound together by collagen fibers, lacking a joint cavity.

Three types of fibrous joints

Sutures, gomphoses, and syndesmoses.

Serrate sutures

Sutures appearing as wavy lines along which bones firmly interlock via interlocking edges (e.g., sagittal suture).

Lap (squamous) sutures

Sutures occurring where two bones have overlapping, beveled edges (e.g., squamous suture).

Plane (butt) sutures

Sutures occurring where two bones meet at straight, nonoverlapping edges (e.g., intermaxillary suture).

Gomphosis

A specialized fibrous joint resembling a nail hammered into wood; anchors a tooth into its bony socket.