A The epidermis accounts for the major part of the skin.
B The majority of epidermal cells are keratinocytes.
C Melanocytes are cells found in the dermis.
D Sweat glands are of two types: eccrine and apocrine.
B The majority of epidermal cells are keratinocytes.
C Melanocytes are cells found in the dermis.
D Sweat glands are of two types: eccrine and apocrine.
E Adnexal structures span the epidermis and dermis.
1. B, D, E
The epidermis accounts for 5 per cent of the total skin, while the dermis accounts for 95 per cent.
The epidermis accounts for 5 per cent of the total skin, while the dermis accounts for 95 per cent.
The epidermis is composed of keratinised, stratified, squamous epithelium. From superficial to deep it has five layers: stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum and stratum basale. The dermis consists of a superficial papillary layer and a deeper reticular layer.
The majority of epidermal cells are keratinocytes. The basal epidermis also contains melanocytes. Keratinocytes are classified according to their depth and degree of differentiation.
Melanocytes originate from the neural crest and are found in the basal epidermis. Each melanocyte synthesises the pigment melanin, which protects the cell nuclei from ultraviolet radiation. The keratinocytes in the strata granulosum and spinosum contain the melanin.
Differences in skin colour are determined by variations in the amount and distribution of melanin within the keratinocytes.
The sweat glands, eccrine and apocrine, open into pores in the hair follicles. Eccrine glands are present throughout the entire body surface, except for the lips. They secrete sweat in response to sympathetic activity such as emotion and are responsible for thermoregulation. In hyperhidrosis, where there is excessive sweating (commonly seen in the palms, axilla and lower limbs), the condition can be cured by performing a sympathectomy. Apocrine glands are found in the axillary and groin areas and become active at puberty. Persistent infection of these glands causes hydradenitis suppurativa.
Adnexal structures, such as hair follicles, sebaceous and sweat glands, span epidermis and dermis. In injuries where epidermis is lost, re-epithelialisation occurs from these structures.
Differences in skin colour are determined by variations in the amount and distribution of melanin within the keratinocytes.
The sweat glands, eccrine and apocrine, open into pores in the hair follicles. Eccrine glands are present throughout the entire body surface, except for the lips. They secrete sweat in response to sympathetic activity such as emotion and are responsible for thermoregulation. In hyperhidrosis, where there is excessive sweating (commonly seen in the palms, axilla and lower limbs), the condition can be cured by performing a sympathectomy. Apocrine glands are found in the axillary and groin areas and become active at puberty. Persistent infection of these glands causes hydradenitis suppurativa.
Adnexal structures, such as hair follicles, sebaceous and sweat glands, span epidermis and dermis. In injuries where epidermis is lost, re-epithelialisation occurs from these structures.
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