AN72.1-AN73.3 | Integumentary System — Glossary

The outermost layer of skin; stratified squamous keratinised epithelium derived from ectoderm with five layers (basale, spinosum, granulosum, lucidum, corneum)

The deepest epidermal layer; a single row of cuboidal/columnar stem cells attached to the basement membrane by hemidesmosomes; also contains melanocytes

The prickle cell layer; 8-10 layers of polyhedral cells connected by desmosomes; contains Langerhans cells for immune surveillance

The outermost epidermal layer; 15-30 layers of flat, anucleate, keratin-filled dead cells (corneocytes) forming the physical and waterproof barrier

The predominant cell type of the epidermis; produces keratin as it migrates from basale to corneum; transit time approximately 28 days

A dendritic cell in the stratum basale derived from neural crest; synthesises melanin in melanosomes and transfers pigment to surrounding keratinocytes

A dendritic antigen-presenting cell in the stratum spinosum; part of the immune surveillance system; derived from bone marrow monocytes

The connective tissue layer of skin deep to the epidermis; divided into papillary (loose CT) and reticular (dense irregular CT) layers

An encapsulated mechanoreceptor in dermal papillae detecting fine/discriminative touch; concentrated in fingertips, lips, and eyelids

A large encapsulated mechanoreceptor in the deep reticular dermis and subcutaneous tissue detecting deep pressure and vibration

The complete set of chromosomes of an organism arranged by size, centromere position, and banding pattern; normal human: 46,XX (female) or 46,XY (male)

The constricted region of a chromosome where sister chromatids are joined and kinetochore proteins attach to spindle microtubules during cell division

Repetitive TTAGGG sequences at chromosome ends that protect against degradation and end-to-end fusion; shorten with each cell division (cellular ageing clock)

A chromosome with the centromere near one end, creating a very short p arm; human acrocentric chromosomes: 13, 14, 15, 21, 22 (carry NOR for rRNA)

A chromosome banding technique using trypsin and Giemsa stain producing a unique pattern of dark and light bands for chromosome identification

The condensed inactive X chromosome visible as a dark dot at the inner nuclear membrane; number of Barr bodies = number of X chromosomes minus 1

The principle that in female somatic cells, one X chromosome is randomly inactivated early in development (Mary Lyon, 1961); ensures dosage compensation

X-inactive specific transcript; a long non-coding RNA expressed from the inactive X that coats the chromosome and recruits silencing factors

The mechanism ensuring equal X-linked gene expression between XX females and XY males by inactivating one X chromosome in each female cell

A holocrine gland opening into hair follicles; entire cell disintegrates to form sebum (lipid-rich secretion); part of the pilosebaceous unit

A simple coiled tubular gland with merocrine secretion producing hypotonic sweat for thermoregulation; present over entire body surface

An autoimmune blistering disease caused by IgG antibodies against desmoglein 3 in desmosomes of stratum spinosum; intraepidermal acantholysis