Identify and describe the three layers of the skin
- Epidermis: the thin outer layer of the skin that consists of keratinocytes that are responsible for structure & barrier, while melanocytes are responsible for the epidermis’s production of melanin
- Dermis: the middle layer of the skin that consists of two parts, the papillary dermis (thin, upper layer) while the reticular dermis (thick, lower layer)
- Hypodermis (subcutaneous fat layer): deepest layer of skin made up of fat and connective tissue
Identify and describe the five layers of the epidermis
- Stratum corneum: the outermost layer of the epidermis, consisting of dead cells that have been flattened and filled with keratin.
- Stratum lucidum: a thin, clear layer of dead skin cells.
- Stratum granulosum: a thin layer of cells that contain granules of keratin.
- Stratum spinosum: several layers of keratinocytes held together by desmosomes.
- Stratum basale: a single layer of cells primarily made of basal cells.
Identify and describe the four major cell types in the epidermis
- Keratinocytes: forms a physical barrier against environmental damage from UV rays, keratin production and waterproofing
- Melanocytes: melanin is produced in the stratum basale
- Intraepidermal macrophages (Langerhan’s cell): immune cells that protect against pathogens and are found in deeper strata of the epidermis
- Tactile epithelial cells (Merkel cells): respond to light touch and are found in the deepest strata of the epidermis
Describe conditions that arise when there is a disruption in homeostasis of these
cells
Albinism: a group of inherited disorders characterised by little or no melanin production. caused by mutations in specific genes that are responsible for the production of melanin. Oculocutaneous Albinism (OCA) affects skin, hair and eyes & Ocular Albinism (OA) affects eyes
Vitiligo: a skin disorder where patches of skin lose their pigment, resulting in irregular white patches. Some possible causes are autoimmune response, genetic factors, oxidative stress and neural.
Describe the sensory function of the skin
Mechanoreceptors respond to physical changes.
- hair follicles: light touch
- meissner corpuscles: indentation and slipping
- pacinian corpuscles: vibration
- merkel complexes: texture understanding
- ruffini corpuscles: stretch
Themoreceptors: respond to changes in temperature.
Nociceptors: help signal pain that is related to temperature, pressure and chemicals
Describe the components and functions of the dermis, with specificity to the two division
The dermis is composed of connective tissue containing collagen and elastic fibres, containing two regions:
1. Papillary region: lies below the epidermis and houses capillaries, responsible for formation of fingerprints, releases growth factors for epidermal cell growth and differentiation.
2. Reticular region: dense irregular connective tissue with thick bundles of collagen and elastin fibres, secures the skin, and contains Pacinian corpuscles that sense pressure, vibration and pain.
Describe the components and function of the hypodermis
Hypodermis attaches the skin to underlying tissues and organs. Insulates body, protects body from harm, storage of energy and connecting skin to muscles and bones.
Describe the structure and function of the hair
Structure:
Hair is composed of dead, keratinized epidermal cells, and genetics determine the thickness and distribution. The parts of a hair include
- shaft (above skins surface)
- the follicle (below the level of the skin)
- a root that penetrates into the dermis
The dermis includes:
- an epithelial root sheath
- a dermal root sheath
Function:
- protection (e.g. from UV radiation, foreign particles in the nasal passage and ears)
- sensory function - feel light touch
- thermoregulation - trap of warm air close to the skin
- communication - different hair styles, colours etc
Describe the lifecycle of hair (hair growth)
- Anagen Phase (Growth Phase):
Active phase of hair growth, during which the hair follicle is producing new cells and hair shaft. - Catagen Phase (Transition Phase):
The catagen phase is a relatively short transitional phase that follows the anagen phase. During this phase, the hair follicle shrinks and detaches from the hair shaft.
This phase lasts for about 2 to 3 weeks. - Telogen Phase (Resting Phase):
In the telogen phase, the hair follicle is at rest and no longer actively producing new hair.
Old hair is held in place by the follicle, and a new hair begins to form beneath it. This phase can last for around 2 to 4 months.
Name and describe the major glands in the integumentary system
Sebaceous Glands:
Sebaceous glands are associated with hair follicles and secrete an oily substance called sebum. Sebum helps moisturize and protect the skin and hair.
These glands are most abundant on the face, scalp, and upper back
Eccrine sweat glands
- all over the body, open directly to the outside through pores
- clear, watery sweat
- generally odourless unless bacteria break down its components on the skin surface
- regulate body temperature
- functional from birth
Apocrine Sweat Glands:
- mainly found in the armpits, around the nipples and the genital area
-produces a thick, milky sweat that contains fats and proteins
-produces odour when broken down by skin bacteria
- scent communication and may serve as a pheromonal signal
- activated by emotional stress and hormonal changes, especially during puberty
- active around puberty
- larger than eccrine glands and open into the hair follicle just before it opens onto the skin surface.
Ceruminous Glands:
Ceruminous glands are specialized sweat glands located in the ear canal. They secrete cerumen, commonly known as earwax. Cerumen helps to lubricate and protect the ear canal, trapping dust and foreign particles.
Describe wound healing and differentiate between the two major types
Wound healing is the process by which the body repairs and regenerates damaged tissue after injury.
- Epidermal wound healing occurs following superficial wounds that affect only the epidermis.
- Deep wound healing occurs when an injury extends to the dermis and subcutaneous layer in three major stages:
- inflammation
- proliferative
- remodeling
Explain what causes aging in the integumentary system
- wrinkles develop
- dehydration and cracking occurs
- sweat production decreases
- a decrease in the numbers of functional melanocytes results in gray hair and atypical skin pigmentation
- subcutaneous fat is lost, and there is a general decrease in skin thickness
- nails may also become more brittle
Describe the classifications of burns
A burn is a tissue damage caused by excessive heat, electricity, radioactivity or corrosive chemical that denature the proteins in skin cells. Burns are graded according to severity.
- First-degree burn - epidermis affected
- Second-degree burn - epidermis and dermis affected
- Third-degree burn - epidermis, dermis and subcutaneous layer affected
structure and function of nails?
made of keratinized epidermal cells and include a free edge, a transparent nail body with a whitish lunula at its base and a nail root embedded in a fold of skin.
functions include protecting the digits and contributing to tactile sensation.
what are the three phases of wound healing?
- Inflammatory phase (hemostasis stage)
- stabilisation and cessation of bleeding in the wounded area
vasoconstriction, platelets adhere to the exposed collagen and other components at the injury site
- acute inflammation stage: release of cytokines and growth factors and migration of leukocytes to the wounded region - proliferative phase
- enhanced migration of keratinocytes, fibroblasts, endothelial cells, and leukocytes to the wound area
- boost in the production of extracellular matrix components - laying down of collagen type III proteins
- enhancement of angiogenesis (formation of new blood vessels)
- improvement in re-epithelialisation mechanisms (recovery of the surface layer - like in epidermal wound healing). - remodelling phase
- surge in the activity of matrix metalloproteinases (MMPs)
- replacing collagen type III with collagen type I
- initiation of apoptosis for provisional endothelial cells, fibroblasts, and myofibroblasts in the wound
what is the rule of nines?
the rule of nines is used to estimate the surface area of an adult affected by a burn. the body is divided into segments representing 9% or multiples of 9%
- head and neck - 9%
- each arm - 9%
- front of torso - 9%
- back of torso - 9%
- each leg - 18%
- perineum - 1%
