Integumentary system: anatomy, physiology and function of skin Flashcards
1
Q
skin composed of 2 main layers
A
- epidermis
2. dermis
2
Q
subcutaneous layer is found beneath dermis and is not considered part of skin. T/F?
A
True
3
Q
Skin
A
- largest organ in the body
- approx. 16% of total body weight of adult
- weighs twice as much as brain
4
Q
epidermis
A
- composed of stratified keratinized squamous epithelium
5
Q
epidermis is made up of 4 main types of cells
A
- keratinocytes (90% of cells in this layer)
- melanocytes (8% of epidermal cells)
- responsible for producing pigment (melanin)
- langerhans: involved in immune response
- merkel cells: function in sensation of touch
6
Q
epidermis is avascular (without blood vessels) and is dependent on blood vessels of dermis for:
A
- oxygenation
- metabolite provision
- removal of metabolic wast products
7
Q
epidermis layers
A
- stratum basale: deepest layer
- stratum spinosum (prickle cell layer)
- stratum granulosum (granular layer)
- stratum lucidum (finger tips, palms and soles)
- stratum corneum (top layer)
8
Q
Stratum basale
A
- made up of single row of columnar keratinocytes
- melanocytes and Merkel cells found within this layer
- only layer within epidermis that consists of cells capable of division
- nearest layer to dermis and located under epidermis
- dermis contains blood supply and provides nourishment to stratum basale
9
Q
keratin
A
- fibrous protein
- protects skin from heat, chemicals and microorganisms
10
Q
melanocytes
A
- produce melanin
11
Q
melanin
A
- pigment that protects skin from harmful effects of ultraviolet (UV) light
12
Q
Merkel cells
A
- make contact with flattened process of a sensory neuron called a Merkel disc.
- merkel cells + discs detect sensation of touch
13
Q
Stratum spinosum
A
- daughter cells of keratinocytes lose their ability to divide in this layer
- they become rounder and ‘spikier’ in shape
- daughter cells join together via desmosomes
- this arrangement contributes to tensile strength and flexibility of skin
- langerhans cells found here
14
Q
Langerhans cells
A
- developed from specialized dendritic cells of immune system
- also found in dermis, lymph nodes and thymus
- produced in red bone marrow
- migrate to stratum spinous and participate in immune responses against microorganisms
- function: attracting and phagocytosis microbes and presenting their antigens to T lymphocytes (activating them to destroy microbes)
- crucial in helping other cells of immune system to recognize invading microorganisms and destroy them
15
Q
Stratum granulosum
A
- cells become longer and flatten horizontally to form this layer
- cells go through apoptosis here
- cells lose their nucleus and become keratinized and comprised entirely of tough pliable protein – keratin
16
Q
keratohyalin
A
- present in stratum granulosum
- consists of darkly staining proteins that convert monofilaments to keratin
- Odland’s bodies may be seen
17
Q
Odland’s bodies
A
- membrane-coating, lamellar granules that produce lipid, which extrudes into the spaces btwn the cells and helps them stick together
18
Q
Stratum lucidum
A
- only found in areas where skin is thick (e.g. palm and soles)
- contains clear, dead keratinocytes that are flattened + large amounts of keratin + thickened plasma membranes.
- lies btwn stratum granulosum and stratum corneum
- provides some degree of waterproofing to skin
19
Q
Stratum corneum
A
- uppermost layer
- cells are arranged in orderly, vertical stacks
- cells contain protein keratin
- intracellular lipid from lamellar granules in stratum granulosum cements cells together and vital in preventing cells from drying out
- as cells move through here, they lose their stickiness and are shed singly or in clumps (squamae)
20
Q
callous
A
- abnormal thickening of the stratum corneum
21
Q
dermis
A
- lies below epidermis and above subQ layer
- responsible for providing nutrients and physical support to epidermis
- contains lymph vessels, nerve endings, hair follicles, and glands
22
Q
blister
A
- when dermis and epidermis become separated as a result of shearing forces or friction, allowing fluid to collect
23
Q
dermis composed of 2 layers:
A
- reticular layer
2. papillary layer
24
Q
papillary layer
A
- contains the nerve and capillaries that nourish epidermis
25
reticular layer
- made up of strong connective tissue containing collagen and elastic fibers
26
collagen and elastin
- arranged in network of fibers that have significant tensile strength providing dermis with ability to stretch and contract
27
collagen
- protein that contributes to approx 70% of dry weight of dermis
28
collagen fibers
- when skin is stretched, these fibers prevent tearing as result of their high tensile strength
29
elastin fibers
- synthesized by fibroblasts
| - finer than collagen and found woven among collagen bundles
30
elastin
- has elastic properties that allow skin to return to its normal position after stretching
31
with age:
- reduction in number of collagen fibers , which stiffen and break up
- results in collagen fibers losing their shape and becoming tangled
- elastin fibers lose some of their elasticity, thicken into bundles and fray
32
glands in dermis (sweat glands)
- 3-4 million sweat glands
| - function: release sweat into hair follicles or on to skin surface through pores
33
2 types of sweat glands
1. eccrine glands
2. apocrine glands
- based on their structure, location and type of secretion
34
Eccrine glands
- simple, coiled glands
- specifically in skin of forehead, palms and soles of feet
- produce sweat
35
sweat composed of:
- water
- sodium and chlorine ions
- urea
- uric acid
- ammonia
- amino acids
- glucose
- lactic acid
36
sweat glands
- have important role in thermoregulation through evaporation
37
Apocrine glands
- not active during childhood
- activated by sex hormones during puberty
- simple coiled tubular glands
- mainly found in axillae, groin, areolae of breasts, and bearded regions of face
- unlike eccrine glands, sweat produced is slightly viscous with milky or yellowish appearance
- this sweat has no smell when it leaves the gland
- however when bacteria metabolize sweat components to produce musky odor (body odor)
38
Sebaceous glands
- simple branched acinar glands
- most are connected to hair follicles
- commonly found on face, neck and back
- secrete sebum
39
acinar gland
- gland that has a sac-like secretory unit and an obvious lumen
40
sebum
- oily substance composed of a combination of triglycerides, cholesterol, proteins and organic salts
- covers surface of hairs and protects them from drying and becoming brittle
- inhibits excessive evaporation of water from skin so that skin remains soft and supple
- lubricant
- has anti fungal and antibacterial properties
41
blackheads
open comedones
42
whiteheads
closed comedones
43
Ceruminous glands
- found in external ear
- modified sweat glands
- these glands produce waxy lubricating secretion
- this + secretions from sebaceous glands produce a yellowish substance called cerumen
44
cerumen
- yellowish substance formed by combo of secretions from ceruminous and sebaceous glands
- function: provide sticky barrier to inhibit entrance of foreign bodies and insects into the ear
- also prevents bacteria and fungi from entering cells because of its waterproofing ability
45
2 main networks of cutaneous arteries
1. deep plexus (network of blood vessels) found where dermis and subQ fat layer join
2. superficial plexus
46
deep plexus
- supplies dermis and subQ layers of tissue with blood
47
superficial plexus
- branches off and carrie blood vessels to epidermis and dermis boundary
48
hair
- made up of columns of dead, keratinized epidermal cells connected together with extracellular proteins
49
hair shaft
?
50
hair root
- surrounded by a hair follicle
51
hair follicle
- made up of an external and internal root sheath -> together make up the epithelial root sheath
52
epithelial root sheath
external + internal root sheath
53
dermal root sheath
- dermis that encircles hair follicle
54
hair bulb
- base of each hair follicle and surrounding dermal root sheath
- has similar shape to an onion
- contains layer of cells called hair matrix
55
hair matrix
- hair matrix cells arise from stratum basale (layer where cell division occurs)
- hair matrix cells responsible for growth of existing hairs
- also produce new hairs when old hairs are shed
56
3 stages of hair follicle growth cycle
1. growth
2. regression
3. resting
57
growth stage
- cells of hair matrix divide
- new cells added at base of hair so that existing cells are pushed p through half and hair grows longer
- during this process, hair becomes keratinized and dies
58
regression stage
- hair stops dividing
- hair follicle atrophies
- hair no longer grows
59
resting stage
...
60
arrestor pili muscle
- connected to follicle
| - responsible for appearance of goosebumps
61
finger and toe nails
- made of sheets of keratin and are tough
- function: protect ends of the digits and allow performance of intricate movements
- grow from germinal cells called nail root
62
nail root
- germinal cells where nails grow from
63
hyponychium
- the tip of the finger, lying beneath distal end of the nail
- area of thickened epidermis that allows for greater protection of the digit ends
64
functions of skin
- sensation
- thermoregulation
- protection and synthesis of vitamin D
