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physio lab-5

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9-l
The Skin
Th.: skin is the pri mary organ of the intexumemary system
and i~ the largest organ of the body. Forming the outer
protecti ve covering of the hody. the skin is a rontinuous
sheet of cutaneous rncmhrunc.
Before You Begin
D Read the appropriate chapter in your textbook.
tJ Set your learning goals. Whe n you fini sh this exerci se.
you should be able to:
• describe the major structures of the skin and identify
their functions
• identify important skin structures in a diagram, model,
and prepared spcdml'n
• romparc and l'Olltr.i,t lt:ature~ of th il·k ~kin and thin
0
\kin
D Prepare your matenab:
• model or chan of a skin cros~ ~el· tion
• microscope
• prepared microslides:
thin skin section
thick skin .1ectio11
l111ir fol/ ic/1'1 1·. 1·.
D Carefully reaJ the directions anJ safely tips for this
exercise before ~taning any procedure.
A. Basic Skin Structure
First in a model, then in prepared microscopic spc:dmcns.
identify the elements of skin structure iJcntified in the
following steps.
·
.1
·: · SAFETY·FIRST!
... .
□ 2
.
Don't forget the rules for safe uu of the microscope.
□
1
The -skin has two distinr.:t layers. The superficial layer
is a sheet of keratinizcd stratified squamous
epithelium called the epidermis. The epidermis is
it~elf Jiviued into distinct histological regions, or
strata (rneaning "layers''):
• Stratum basale is the deepest stratum of the
epiuermis. It consists of a single sheet of
columnar cells that continue to divide. As the
daughter ~ells are formed, they are pushed
upward, becoming part of the next stratum.
• Stratum spinosum is noted for its multilayer of
distoneu ("spined") cells. The cells become
distoned as they are pushed up from the deeper
stratum basale and look somewhat "spiny" when
stained and prepared for microscopy. Stratum
basale and stratum spinosum together are often
l·allcJ stmt11m xer111i11ativ11m.
• Stratum granulosum is superficial to strntum
spi1Hhlllll. It l 0l1tai11s tl,ltll'IH.:d ,·t:11_, pw,hed 11r
from thr dl'q'k.·r ~trata. ,\, thl· n ·II, :in: pw,h,•d up
1lm111µh th1, ,trat11111, thl')' ll1r111 lhl' p1111cin
_.: ranulc, that give 11 the name grww/0 111111. By the
time.: the l'ells lca\'e 1hi~ stratum. they have died.
• Stratum lut'idum tnll·aning "'light b)1..•r"'1 is a very
1h111 !.1yi:r prl'Sl'llt only in thick skin. Thil·k ,kin is
founu only in high-wear areas such as the palms
and soles. The more fle xible thin skin i~ found
over mlist other areas of the bo<ly. This stratum's
name rnmes from the far.:t that it is translucent,
allowing light to pass through it easily.
• Stratum corncum b the layer of deaJ,
keratinized tis~uc alreaJy identif\l'd in Lah
EKl'rrise 5. Stratum rnrucum is extrt·mely thick
in thi1,:k !skin. providing a gre<1t ,kal of
prntel·fi,m. Stratu111 c.:ornt·um pnitel·ts tkl.'per
tissues fro111 med1anil'al injury, inward or
outwarJ Jiffusion \lf wutcr um! other 111okr.:ules,
and inva~ion by minuorganism~.
The layer of skin deep to the cpidcnni~ is a sheet of
irregular fibrous connective tissue calleJ the dermis.
The dermi~ is usually much thicker than the
epidermis. Like most conne1:tivc tissues, the Jem1is
has a scattering of blood vessels and nerves. The
blood vessds supply both the dcm1is and epidcnnis.
Bcr.:ause blood cools when it travels through the skin,
1hc body varies the amount of blood sent to the skin ·
to n.:gulate loss of heut by the entire body. The dcnnis
contains many sensory nerve endings. Se nsations
such as heat, cold. touch. and pressure are mediated
57
■
o
hy dermal nerve endings. The~ arc two regions of
the dermis:
• The rttlculur luyer of 1he dermis is u thick
region of irregularl y urrangctl protein fibers.
Most of the fibcri, arc collage nous, but a few are
made of d a~tin.
• The papillary layer is the bumpy supe~cial .
portion of the dermis attached to the ep1dcnrns.
The bumps. called papillae (meaning ."nipples"),
form regular rows in thick skin but ate rather
irregularly arranged in thin skin. For this reason,
thick skin can be observed to have distinct
ridges. such as fingerprints. These ridges give the
hands and feet better gripping ability.
3 Deep to the skin is a layer of subcutaneous tissue, ·
sometimes called the hypodermls or supertlclal
fascia. Although not a part of the skin, it is often
studied along with skin. Subcutaneous tissue is loose,
fibrous (areolar) connective tissue that connects the
~kin to underlying muscles and bone. Some of the
areolar tissue has been modified to become adipose
tissue. Adipose tissue's protective and insulating
characteristics complement the protection and
temperature regulation roles of the skin.
Hint. . . Minircfercnce Plate 7 shows light micrographs
of 1kin suucturc,. Plate 7a represents thin skin, Plate 7b thick
skin, Plate 7c thin skin with hair follicles and other accessory
structures, and Plate 1d thin skin with sweat glands.
B. Hair, Nails, and Glands
The skin has a variety of accessory structures, including hair
and nails. Both hair and nails are modified forms of stratum
corneum, or keratini~ed tissue. Hair is a cylinder of compact
keratinized material, and a nail is a plate of compact
keratinizcd material. Identify the structures described here in
a model and in prepared specimens.
D
1 Each hair is formed within a separate hair follicle.
The follicle is a sheathlike indentation of the
epidermis. At the bottom of the follicle, a hair
'
. h tratum genninativum produces
11
papilla covered ~ sf each hair within the follicle is
. Th poruon o
.
h
the hair. e
hcreas the part1on thut as
•
hulr
root,
w
·
h
l
rn II cd thc
of the follicle is called the a r
been pushed ~ut
dense cortex and a less
shaft. The hair has a very
dense medulla. h ~ tr cle is an exocrine (ducted) ,
Attached to cac o i_ land produces the fatty
sebaceous glaDd , This g
h hair and skin
substance sebum, that coats l e
..
th. h .
'
.sture loss and conditions e au
Sebum prevents mm.
.
d
·1
.
.
h·
t
·1 docsn 't become bnttle an eas1 y
1
and skm sot u
•
broken.
th
1
0 3 The arrector pili muscle is a stra~ of smoo muse e
tissue connecting the side of a follicle to the
superficial surface of the dennis (fig. 9.1 ). Wh~n.
contracted, the muscle pulls the follicle so th~t.it is
nearly perpendicular to the skin's su~ace: This .
increases the air spaces among the hairs, 1mprovm_g_
its insulation quality. Contra~tion of the arrector p1h
also dimples the epidermis, raising a ridge at the edge
of the follicle (a "goosepimple").
n 4 The toenail or fingernail is also formed by a modified
portion of stratum germinativum. In the case of either
hair or nail, this modified tissue is often called
matrix. A portion of the nail bed (skin under the
· nail) is matrix that produces the nail plate. Part of tht
matrill may be visible through the nail as a pale
crescent, or lunula. Nail formation begins under a
fold of epidermis. The portion of the nail under the
fold is the root, and the visible portion is the nail
body. A cuticle, or eponychium, may extend from
the fold onto the nail body (fig. 9.2).
D S Sweat glands are _found in many areas of the skin.
They are exocrine glands that produce a watery
solution, sweat, that coats the skin. Sweat serves
primarily to improve heat loss by the sk.in through
evaporation. Eccrine sweat glands produce thin,
watery sweat in many areas of the body. Apocrine
~weat glan~s. found in the axillary and pubic regions,
. secrete a thicker sweat that is rich in complex organic
molecules.
Review what you have learned about skin by comp) t' g
figure 9.3.
em
□ 2
by dermal nerve endings. There are two regions of
the dermis:
• Thl· reticular luyer of the dermis is a thick
region of irregularly arranged protein fibers.
Most of the fibers arc collagenous, but a few are
made of elai.tin. '
• The papillary layer is the bumpy superficial
portion of the dennis attached to the epidermis.
The bumps, called papillae (meaning "nipples"),
form regular rows in thick skin but are rather
irregularly arranged in thin skin. For this reason.
thick skin can be observed to have distinct
ridges, such as fingerprints. These ridges give the
hands and feet better gripping ability.
D 3 Deep to the skin is a layer of subcutaneous tissue, .
sometimes called the hypodcrmls or superfklal
fascia. Although not a part of the skin, it is often
studied along with skin. Subcutaneous tissue is loose.
fibrous (areolar) connective tissue that connects the
skin to underlying muscles and bone. Some of the
areolar tissue has been modified to become adipose
tissue. Adipose tissue's protective and insulating
characteristics complement the protection and
temperature regulation roles of the skin.
·11 covered with stratum germinativum produces
papi 8
·
· h'
h f 11· I .
the hair. The portion of each hair wit _m t e o ic e is
rnlkd the hulr root, whereas the portion that has
been pushed out of the follide is called the hair
shaft. The hair has a very dense cortex and a less
dense medulla.
Attached to each follicle is an exocrine (ducted) ,
sebaceous gland. This gland produces the fatty
substance, sebum, that coats the hair and skin.
Sebum prevents moisture loss and conditions the hair
and skin so that it doesn't become brittle and easily
broken.
□ 3 The arrector pili muscle is a strap of smooth muscle
tissue connecting the side of a follicle to the
superficial surface of the dermis (fig. 9.1 ). When
contracted, the muscle pulls the follicle so that it is
nearly perpendicular to the skin's surface. This
increases the air spaces among the hairs, improving
its insulation quality. Contra~tion of the arrector pili
also dimples the epidermis, raising a ridge at the edge
of the follicle (a "goosepimple").
n 4 The toenail or fingernail is also formed by a modified
portion of stratum genninativum. In the case of either
hair or nail, this modified tissue is often called
matrix. A portion of the nail bed (skin under the
nail) is matrix that produces the nail plate. Part of the
Minircfcrcncc Piute 7 shows light micrographs
matrix may be visible through the nail as a pale
of skin structures. Plate 7a represents thin skin, Plate 7b thick
crescent, or lunula. Nail formation begins under a
skin, Phatc 7c thin skin with hair follicles and other accessory
fold of epidermis. The portion of the nail under the
structures, and Plate 7d thin skin with sweat glands.
fold is the root, and the visible portion is the nail
body. A cuticle, or eponychium, may extend from
the fold onto the nail body (fig. 9.2).
D 5 Sweat glands are _found in many areas of the skin.
They arc exocrine glands that produce a watery
solution, sweat. that coats the skin. Sweat serves
The skin has a variety of accessory structures, including hair
and nails. Bo~h hair and nails are modified forms of stratum
primaril~ to improve heat loss by the skin through
corneum, or keratinized tissue. Hair is a cylinder of compact .
evaporation. Eccrine sweat glands produce thin,
keratinized material, and a nail is a plate of compact
watery sweat in many areas of the body. Apocrine
keratinized material. Identify the structures described here in
sweat glan~s. found in the axillary and pubic regions,
a model and in prepared specimens.
. secrete a thicker sweat that is rich in complex organic
molecules.
0 1 Each hair is formed within a separate hair follicle.
Review what you have learned about skin by completing
figure 9.3.
The follicle is a shcathlike indentation of the
epidennis. At the bottom of the follicle, a hair
Hint. ..
B. Hair, Nails, and Glands
□ 2
Contracted
~igure 9.1
When the arrector pili contracts, it pulls the follicle and hair into a perpendicular position, improving the
nsulation quality of the hair. Notice how a "gooscpimple" is raised around the follicle opening.
2
3
4
5
Figure 9.2 Label this ~ec.:tion of a finger with the appropriate terms.
59
9-4
The Skin
EPIDERMIS
~~·u·Llt1/,a~U'liJJlMJ ©CQ)fRlWJ~lUJlMl 1
~iJ'lR1ffeiiJ'll1l~ [1,lVJ©[email protected]!lfl~ 2
~· lflxli~u'QJJ!Ml @~[N](lJ)[L©~lVJ~
~tf~"fflVJ~ [email protected]~lVJ~ 4
@tf'MiJ'lVJIM! ~~~ffi\[L[g s
3
5
DERMIS
[j2)ffi\lP-l0ll~!R1W ~ W[g!Rl 6
!Rl~O©M~!R1 ~W~ 1
®~~If @~INJIQ) 8
@[1,(Q)(Q)IQ) '¥1~~~[1, 9
!NJ (g[R1'¥7[g 10
HAIR
[ru(Q)(Q)lJ' 11
©IXIC\\lN 12
~(Q)[1,[L0©[1,~ 13
~ffi\~ 0[1,~ 14
~;,%if~□~
16
ffi\(R1~~©1f©[R1 ~0[1,0
10
16
®([email protected]\(g[g(Q)lVJ~ @~INJ[Q)
· IXIW[f2)(Q)[Q)~!Ri~U®
. . . . . . Figure 9.3
60
17
10
Use colored pens o r pen.:ils to col or in labels and struc ture~ of (a) thin skin and (b) thicl< skin.
'
The Skin
Specimen: thin skin section
Total magnification: _ _
Specimen: thick .rkin .rection
Total magnification: _ _
N:Jllll ' - - - - - --- - - - - -- - - - - -- -
Dale _ _ _ _ __ _ __
Specimen: hair follicles c.s.
Specimen: - -- -'---
-
Sl·cri11n
Total magnification: _ _
Total magnification: _
61
Fill-in
Figure 9.2
1.
2.
3.
4.
_ _ _ _ __ __ _ 2
---------- 3
_ __ _ __ _ _ 4
The _]_ is the superficial layer (of two) in the c;ki n.
The hypmlcrmi~ ii- 111ni11ly an:ola, und _ 1_ 11"11c
fingerprint ridges arc formed a~ a result of the orderly arrangement of derma l _1_.
Stratum comeum is composed of dead cell parts and a tough. waterproof protein called
.,
__.___.
_________ 5
Fill-in
__________ 2
'.'i. Strut um _j__ b the cpidcnnal ~tralum in wl11d1 one could find muny phu.-.c~ of mitll-ik
6. Cells are pushed into stratum _.1_ from stratum basale.
7. When you sense cold air around you, nerve endings in the _1_ are probably involved.
8. When you sense cold air around you, bumps may appear on the skin. This is caused by
the contraction of the _.1_.
9. The subcutaneous tissue is also called the superficial fascia, or_]_.
10. Physiologists believe that some sweat glands produce aromatic. organic molecules
called pheromones that may serve sex attractants. The type of sweat gland (of the
two discussed in this exercise) most likely to produce pheromones is __'J__.
11. Strong shampoo tends to remove _1_ from the hair and scalp, making it dry and
eas ily damaged.
12. The eponychium, or_]_, covers part of the oail plate.
13. When you have your hair cut, the portion of the hair trimmed is called the _1_.
14. Blood vessels that supply the ep.idermis are found in the_?_ region of the dermis.
15. Stratum basale and stratum spinosum together may be called stratum_]_.
16. Keratinized --1._ epithelium forms the epidermis. ·
17. The dermis is composed mainly of_?_ fibers. with a few elastic fibers.
18. Stratum --1._ is usually absent in thin skin.
19. _1__ glands produce sebum.
20. The most widely distributed type of sweat gland is the _]_ type of gland.
as
_________ 3
__________ 4
•
---------- 5
_________ 6
__________ 7
_________ 8
__________ 9
10
_ _ _ _ _ _ _ _ _...... 11
- - - - - - - - - 12
__________ 13
Table
Fill in the spaces that are blank.
- - - - - - - - - 14
15
- - - - - - - - - 16
- - - - - - - - - 17
-
Characterbtlc
Epldennls
Tissue type
Presence of
blood vessels
- -- - - - - - 18
- - - - - - - - - 19
- - - - - - - - - 20
Relative
thickness
Permeability
Relative strength
Short answer
Write a few complete sentences.
How docs thin skin di ffer from thick ~kin?
62
l
Dennla ..
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