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PA10315 > Structure of the skin > Flashcards

Structure of the skin Flashcards

1
Q

What is the integumentary system?

A

It’s made up of the skin and its accessory structures, such as hair, nails, glands and sensory receptors.

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2
Q

What is the surface area of adult human skin?

A

1.8-2 metre squared.

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3
Q

What is the range for the thickness of adult skin?

A

0.5 - 4.5mm.

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4
Q

What is the principle function of the skin?

A

To keep water inside of us as the external environment is generally dry.

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5
Q

What are the two main parts of the skin?

A

The epidermis (the top part - 1/10mm thick) and the bottom part, the dermis (1mm thick).

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6
Q

Where is thick skin found?

A

On the palms, tips of fingers, digits and soles of feet.

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7
Q

What are the differences between thick skin and thin skin?

A

Thin skin has hair follicles coming through that are based deep in the dermis. Thin skin is around 1/10mm whereas thick skin can be several mm thick.

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8
Q

What are the type of cells that make up the epidermis?

A

Keratinised, stratified squamous epithelium.

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9
Q

What is the bottom most layer of the skin and what is its function?

A

The stratum basale, it is a single layer of columnar keratinocytes. It is the site of production of new keratinocytes.

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10
Q

What is the second most bottom layer of the skin?

A

The stratum spinosum which is composed of multiple rows of closely packed keratinocytes

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11
Q

What is the third most bottom layer of the skin and its function?

A

The stratum granulosum which is multiple rows of flattened keratinocytes that contain keratohyalin granules and lamellar bodies. These form a hydrophobic, impermeable barrier on release.

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12
Q

What is the second most top layer of the skin?

A

The stratum lucidium which is multiple rows of clear, flat, dead, keratin-rich keratinocytes. It is only present in thick skin.

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13
Q

What is the top layer of the skin?

A

The stratum corneum which is made of multiple rows of dead, flat, enucleate keratinocytes that are made up of cross-linked keratin fibres.

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14
Q

What happens to keratinocytes as they get closer and closer to the surface of the skin?

A

They get further and further away from the “food supply” (blood vessels) and they will eventually begin to die. This is controlled apoptosis.

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15
Q

What is the purpose of the lipid-rich lamellar bodies in the stratum granulosum?

A

It provides an oily layer to prevent water evaporating out of the body.

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16
Q

What are desmosomes and where are they found?

A

A structure that links two adjacent cells. They are found in the stratum spinosum.

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17
Q

How do certain skin diseases arise?

A

There is an imbalance between the formation and death of skin cells. The barrier gets weaker as the turnover is faster than production, for example in psoriasis.

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18
Q

What are keratins?

A

A family of cytoskeletal filament-forming proteins that make up 25-30% of the total protein in the epidermis.

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19
Q

What is the purpose of keratins in the skin?

A

They form branching, rope-like structures in the cell cytoplasm that associate with adjacent cells. They maintain the structural integrity of the epidermis.

20
Q

What is unique about the lipid matrix of the stratum corneum?

A

There are no phospholipids and is mostly composed of ceramides, free fatty acids and cholesterol.

21
Q

What happens to desmosomes when the skin cells die?

A

They get broken down by enzymes.

22
Q

What are Langerhan cells?

A

They are cells that communicate with the immune system and provide a warning system for the skin if harmful substances come into contact, such as poison ivy.

23
Q

What are Merkel cells?

A

Sensory cells that provide a somatic connection to nerve endings such as when something hot is touched.

24
Q

What are Melanocytes?

A

Cells that make melanin and package it into melanosomes.

25
Q

What is the function of melanin?

A

To provide protection against the sun.

26
Q

How are melanosomes transferred to keratinocytes from melanocytes?

A

Epithelial cells phagocytize the tips of the melanocyte and enter the keratinocytes.

27
Q

What does peri-nuclear mean, in terms of melanosomes?

A

The melanosomes surround the nucleus of the keratinocytes to protect them from direct radiation.

28
Q

What are the three types of melanin?

A

Eumelanin, pheomelanin and neuromelanin.

29
Q

What is skin colour mostly dependent on?

A

The amounts of eumelanin and pheomelanin.

30
Q

What are the two regions of the dermis and what proportions are they present in?

A

The papillary (20%) near the top and the reticular (80%) near the bottom.

31
Q

What separates the epidermis and the dermis?

A

The basement membrane (basal lamina).

32
Q

What is the function of the basement membrane?

A

It is a bridging structure and regulates proliferation in the stratum basale and the movement of cells between the dermis and epidermis.

33
Q

What is the purpose of the basement membrane being convoluted?

A

There are more contact points which provides a mechanical benefit.

34
Q

What is the papillary made up of?

A

Elastic fibres and nerve endings - it is a connective tissue.

35
Q

What is the reticular made up of?

A

Dense, connective tissue that is made up of randomly orientated collagen fibres, elastin, proteoglycans and glycosaminoglycans.

36
Q

What are the hairs in the skin composed of?

A

Lots of dead, keratinised epithelium cells.

37
Q

What is the function of the sebaceous gland?

A

It secretes sebum which is a mixture of oily lipids that lubricate the hair shaft.

38
Q

What is horripilation?

A

When hairs stand on end due to the muscle attached to the hair.

39
Q

What are the four stages of hair growth?

A

Anagen, catagen, telogen and exogen.

40
Q

What are glands?

A

Specialised secretory structures formed by epithelial cells.

41
Q

What are the two categories of glands?

A

Endocrine (ductless) and exocrine (with ducts).

42
Q

What are the three modes of secretion from exocrine glands?

A

Merocrine, apocrine and holocrine.

43
Q

What are sebaceous glands?

A

They produce lipid rich sebum.

44
Q

What is the difference between apocrine and eccrine sweat glands?

A

Apocrine glands have limited distribution and are only active from puberty. They are more viscous than eccrine. Eccrine glands are widely distributed and are active shortly after birth.

45
Q

What are the three types of skin sensory receptors?

A

Mechanoreceptors, thermoreceptors and nociceptors.

PA10315 (47 decks)

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