mnsr 24

Question 1

the main functions of the skin

Answer 1

skin provides integument covering and has four main functions
1- protection : tough hide to protect against physical trauma , uv light by the melanin pigment, countinous unbroken line for microorganisms
2- thermoregulation: sweat and hair to provide insulation
3- metabolism: produces vitamin d used for the of calcium and phosphate metabolism
4- sensation: for pain, pressure, and temperature

Question 2

the skin has been an area of

Answer 2

organ of sensory and nervous structure in asctreal metazoan.Embryologically the nervous system arise contiounsly from skin’s ectoderm.

Question 3

Skin is the

Answer 3

largest organ ( 12.5 - 16.7 ) and is continuous w/ urigental tract ( penis/ vagina and urethera ) and digestive tract ( mouth and anus )

Question 4

the two type of the skin

Answer 4

1- glabrous: thick and hairless e.g: soles of the feet and palms
2- hairy: thinner and most skin areas

Question 5

The protective layer of the skin against phsycial chemical and microbial layer is

Answer 5

epidermis ( 0.06-0.1 mm thick )

Question 6

The epidermis arises from

Answer 6

embryonic ectoderm

Question 7

epidermis gives rise to

Answer 7

sweat glands
mammary glands
sebcoutnous glands

Question 8

It predominantly consist of:

Answer 8

keranocytes arranged in stratified squamous epithelium starting at the basal membrane and moves outwards and becomes coreococytes in a process called: desquamation

Question 9

The process of keranocytes maturing to corenocytes in the basal membrane is called

Answer 9

desquamation

Question 10

The entire epidermal cycle takes

Answer 10

27 days

Question 11

The layers of the epidermis from top to bottom

Answer 11

1- stratum corenuem: thick outer layer composed of flattened fused cells and composed mainly of keratin. Corneum is covered with oily secretion from the sebaceous gland called: sebum
2- straum lucidum: only thick skin, clear homogenous, layer without nuclei or organelle.
3- stratum granulosm: showing granules within the cells
4- stratum spinosum: aka prickle layer- growing skin showing early keratin synthesis
5- stratum basale ( basal layer): a proliferative layer of basophilic columnar or cuboidal cells

Question 12

The color of the human skin is due to 3 factors
( skin pigmentation )

Answer 12

1- inherited yellow color from carotene at the subcutaneous fat
2- concentration of oxygenation of the heamoglobin in the dermal capalliries
3- Special branched cells scattered through the stratum basal the pigment in these cells is called: melanin and produces melanocytes. protects us against uv radiation.
A patch of dark pigment on the skin aka mole is called melanocytic nevus and small percentage of it will become cancerous aka melanoma

Question 13

Keratinised structures

Answer 13

• most mammals have: foot pads
• higher primates have: friction ridges on palms and soles of the feet
• the tip of the fingers have fingerprint: dermatoglyph
• nails, claws , hooves are other kerantised structures

Question 14

is an elongated rod of kernatised cells

Answer 14

hair shaft and grows from the root ( the hair bulb ) lying in the dermis layer

Question 15

the hair bulb is the

Answer 15

base of a pit sunk in the dermis called : hair follicle

Question 16

follicle cells is continuous with

Answer 16

epidermis

Question 17

during early —- the —- grows down into the —- to form —-

Answer 17

• early fatal life
• the epidermis
• dermis
• cellular shaft

Question 18

cells of the hair shaft are

Answer 18

dead kernatised epidermal cells expect the base where the growing germinal matrix exists

Question 19

the germinal matrix forms a

Answer 19

cap over a vascularised plug of dermal tissue called the dermal papilla

Question 20

the germinal matrix is connected to the

Answer 20

overlying epidermis by the cellular external root sheath and the entire structure is called: pilosebaceous unit

Question 21

the proliferation in the cells in the germinal matrix produces

Answer 21

hair growth
- initially these cells r pushed up the centre of the epidermal down growth
- as the move further from the papilla blood supply they become kerantized and die
- initial cells transform into: hair cortex w a single outer layer of hair cuticle

Question 22

the hair follicle consist of ( check the structure in the slides )

Answer 22

• medulla ( seldom seen)
• cortex( kernatised cells )
• cuticle( single layer of overlapping kernatised cells )
• internal root sheath: produces further division of germinal matrix cells which pushes up between external root sheath and the hair follicle

Question 23

the hair shaft is help in position from

Answer 23

external and internal root sheath ( ERS AND ERS )

Question 24

Hair grows in a

Answer 24

cyclical basis

Question 25

growth phase in young adult is

Answer 25

~3 years and 85% of scalp hair is in growth phase followed by the degeneration of the follicle.

Question 26

the sebaceous gland is derived from

Answer 26

ERS and produces sebum into the follicle that has mild fungistatic and bacteriostatic action

Question 27

hair position can be elevated bt

Answer 27

arrestor pillus muscle attached to the hair bulb and the epidermis

Question 28

Other glands in the skin

Answer 28

1- sebaceous gland ( oil) 2- sudoriferous gland ( sweat ) 3- ceruminous ( ear wax ) 40 mammary gland

Question 29

is connected to the hair follicle and forms the pilosebaceous unit

Answer 29

-sebaceous gland that produces sebum to protect the skin and the hair. - releases secretions via holocrine mechanisms into the hair follicle shaft - located over most of he body/skin expect palms and soles of the feet

Question 30

The 2 types of sudoriferous ( sweat) gland

Answer 30

1- apocrine - ducts open in the hair follicles asL armpits, pubic region, areola of the breast 2- eccrine: ducts terminate as sweat pores at the epidermis. Throughout the skin except lips,nailbeds, and eardrums - This gland is coiled tubular gland , secretory portion lines fascia within a duct up to the skin surface , secretes sweat for thermoregulation

Question 31

ceruminous glands are

Answer 31

ducts open either directly onto the surface of the external auditory ear canal or into the duct of sebaceous glands. secretion combines w sebum associated w sebcaous gland to from cerumen aka ear wax - to protect the ear from foreign materials as dust

Question 32

are highly modified derivatives of sweat glands

Answer 32

mamamry glands and the milk production is under hormonal control. Mammary glands develop by the thickening of the epidermis - the milk lines - in the abdominal walls

Question 33

dermis is prodmintly composed of

Answer 33

fibroblast which secretes and organises large amount of ECM. ECM is mainly fibrillar collagen as type 1,111, v, elastin

Question 34

papillary dermis is

Answer 34

wish in vasculature and have nerve ending, thermo/cryoreceptors

Question 35

reticular dermis is

Answer 35

- thicker of the 2 substrata - dense connective tissue contains elastin network and proteoglycan - provides structural support for the skin

Question 36

dermis is derived from ---- and is --- in thickness

Answer 36

mesoderm and is 2 mm thick

Question 37

dermis is composed of

Answer 37

- collegen , elastin fibers ( strength and elasticity) - blood vessels ( thermoregulation , immune function - nerves - fibroblast - forms collegen and elastin - mast cells - inflammatory responses to pathogens and injuries - lymphatics - epedrimal appendages - glycosaminoglycan; hyaluronic acid, chondotrion surfaces and glycoprotein ( retains h20 and provides moisture to the epidermis )