Transcript Sweat glands

Chapter 5 b
Appendages of the
Skin
Skin Appendages
• Includes several derivatives of the
epidermis
• Sweat glands
• Sebaceous (oil) glands
• Nails
• Hair follicles
• Hair
Sweat
Glands
Sweat glands
• Widely distributed in skin
• Also called sudoriferous glands
– Sudor = Sweat
• More than 2.5 million per person
Sweat glands
• Different types
– Prevent overheating of the body
– Secrete cerumen (ear wax)
– Secretion of milk
Sweat glands
• Two main types:
– Eccrine
– Apocrine
Eccrine Sweat Glands
• Eccrine glands
• Most numerous, widely distributed
– especially abundant on the palms,
soles of feet, and the forehead
Eccrine Sweat Glands
• Eccrine glands
• Simple, coiled tubular
gland
– Secretory part lies
coiled in the dermis
– Open to skin surface by
ducts (pores)
Sweat Composition
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•
Mostly water (99%)
Some salts (mostly NaCl)
Vitamin C
Antibodies
Dermicidin (a microbe-killing protein)
Lactic acid (attracts mosquitoes)
Sweat Composition
• Traces of metabolic waste
• Small amounts of some ingested
drugs
• Normally sweat is acidic
• pH between 4-6
Sweat Function
• Sweating is regulated by the
sympathetic division of the autonomic
nervous system
• We have little control
• Major role is to prevent overheating
of the body
• Excretes waste products
• Acidic nature inhibits bacteria
growth
Sweat Function
– Heat induced sweating
• helps dissipate excess heat
• Prevents overheating of the body
• Begins on the forehead
– Emotionally induced sweating
(Cold Sweats)
• Brought on by fright,
embarrassment, nervousness
• Begins on palms, soles, armpits
Apocrine Sweat Glands
• Found in the
axillary (arm pit)
and anogenital
areas
• Larger than
eccrine glands
• Ducts empty into
hair follicles
Apocrine Sweat Gland
• Secretion contains same
component as sweat plus fatty
substances and proteins
• Odorless when secreted, but
when decomposed by bacteria
on skin, turns musky – basis of
body odor
• Sometimes has a milky or
yellowish color
Apocrine Glands
• Begins functioning at
puberty
• Becomes active during pain,
stress, and sexual
encounters
• May be analogous to the
sexual scent glands of
animals
Other Sweat Glands types
• Ceruminous glands
–modified apocrine glands in
external ear canal that
secrete cerumen (earwax)
–Deters insects and block
entry of foreign material
Other Sweat Glands types
–Mammary glands –
specialized sweat glands
that secrete milk
–Considered part of the
female reproductive system
Sebaceous (oil) glands
Simple alveolar glands
Found all over the body –
except palms and soles of feet
Small on body trunk and limbs,
but large on face, neck, and
upper chest
Sebaceous (oil) glands
• Produce oil (sebum)
• Lubricants and softens skin and
hair
• Kills bacteria
• Most with ducts that empty into
hair follicles
• Glands are activated at puberty
• Stimulated by hormones
Homeostatic Imbalances
• When a sebaceous
gland duct is
blocked by
accumulated sebum,
it forms a
• If whitehead
whitehead
material oxidizes
and dries, it
darkens to form
a blackhead
Homeostatic Imbalances
• Acne is an active inflammation
of sebaceous glands – usually
caused by a bacterial infection,
often staphylococcus
Homeostatic Imbalances
• Seborrhea (cradle cap) in
infants
– Caused by overactive
sebaceous glands
– Begins on the scalp as pink
raised lesions that gradually
become yellow to brown
• Careful washing to remove
excessive oil often helps
Nails
• Scale-like modification of the
epidermis
• Clear protective covering on the
dorsal surface of the distal part of a
finger or toe (lacks pigment)
• Correspond to the hooves or claws of
other animals
• Contains hard keratin (skin contains
soft keratin)
Nails
• Each nail has
– a free edge
– A body (visible attached portion)
– A root (embedded in the skin)
• Deeper layers of the epidermis
extend beneath the nail as the nail
bed
• Thickened proximal portion of the
nail bed, called the nail matrix
responsible for nail growth
Nails
• Nails appear pink because of
capillaries in the underlying dermis
• Region that lies over the matrix
appears as a white crescent call the
lunula
• Proximal and lateral borders
are overlapped by skin folds
called nail folds
Nails
• Proximal nail fold projects onto the
nail body called the cuticle
• Underneath the free edge is called
the quick
Nail Structures
 Free
edge
Figure 4.9
 Body
 Root of
nail
 Cuticle
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 4.22
Hair Distribution
• Millions of Hairs are distributed
over the entire skin surface
except
– Palms, soles, lips, nipples and
portions of the external
genitalia
Hair Function
• Functions of hair include:
– Helping to maintain warmth (more
so in other mammals)
– Alerting the body to presence of
insects on the skin (main function)
– Guarding the scalp against physical
trauma, heat loss, and sunlight
Hair Function
• Functions of hair include:
– Eyelashes shield the eyes
– Nose hairs filter large
particles like lint and insects
from the air we breath
Structure of Hair
• Filamentous and flexible strands of
dead keratinized cells produced by
hair follicles
• Made up of the shaft projecting from
the skin, and the root embedded in
the skin
• Contains hard keratin
– which is tougher and more durable
than soft keratin of the skin and
does not flake off
Structure of Hair
• If shaft is flat and ribbonlike in
cross section, the hair is kinky or
curly
Structure of Hair
• If shaft is oval,
hair is wavy
Structure of Hair
• If shaft is
round, hair is
straight and
tends to be
course
Produced by
hair bulb
Hair
Consists of
hard
keratinized
epithelial
cells
Melanocytes
provide
pigment for
hair color
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 4.7c
Slide 4.18
Structure of Hair – 3 layers
• 1. Medulla 2. Cortex
3. Cuticle
• Medulla
– Central core
– Consists of large cells and air
spaces
– Absent in fine hairs
Structure of Hair – 3 layers
• 1. Medulla 2. Cortex
3. Cuticle
• Cortex
– Bulky layer surrounding the
medulla
– Several layers of flattened cells
Structure of Hair – 3 layers
• 1. Medulla 2. Cortex
3. Cuticle
• Cuticle
– Outermost layer
– Single layer of overlapping cells
The hair shaft
consists of a core
called the medulla,
a cortex, and an
outermost cuticle
Figure 5.6a
• Hair conditioners smooth out rough
surface of cuticle to make hair look
shiny
• Cuticle tends to wear away at the
tip of the hair shaft, allowing the
keratin fibrils in cortex and medulla
to frizz out, creating ‘split ends’
Color
• Pigmented by melanocytes at
the base of the hair
• Gray or white hair results from
decreased melanin production
and from the replacement of
melanin by air bubbles in the
hair shaft
Hair Follicle
• Root sheath extending from the
epidermal surface into the dermis
• Deep end is expanded forming a hair
bulb
• A knot of sensory nerve endings (a
root hair plexus) wraps around each
hair bulb
• Bending a hair stimulates these
endings, hence our hairs act as
sensitive touch receptors
Hair Follicle
Figure 5.6c
Associated Hair Structures
 Hair follicle
Dermal and
epidermal sheath
surround hair root
 Arrector pilli
Smooth muscle
 Sebaceous gland
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 4.7a
Slide 4.20
Types of Hair
• Vellus – pale, fine body hair
found in children and the
adult female
• Terminal – coarse, long hair
of scalp, eyebrows, axillary
(armpit), and pubic regions
Hair Growth
• Rate of hair growth – 2.5 cm per week,
but varies some with age and gender
• Each follicle goes through growth
cycles
• Active stage – active growth, last
from weeks to years
• Regressive stage – Hair matrix cells
die, hair bulb shrivels somewhat
• Resting stage – lasts one to three
months
Hair Growth
• After resting stage, the matrix
proliferates again and forms a new
hair to replace the old one that has
fallen out or will be pushed out by
the new hair.
• We lose about 90 scalp hairs daily
• Follicles of eyebrows only stay
active 3 to 4 months, which is why
eyebrows are not as long as the hair
on our heads
Hair Thinning & Baldness
• Alopecia
– hair thinning in both sexes
(as we age)
• True, or frank, baldness
– Genetically
determined and
sex-influenced
condition
– Male pattern
baldness is most
common
• Other causes of hair loss or thinning
– Fever, surgery, severe emotional
trauma, drugs, protein-deficient
diets
• Hirsutism =
excessive hairiness
– In women may be
the result of an
adrenal gland or
ovarian tumor
Rosacea
• Usually on cheeks or nose
• Begins as a sudden flushing of the skin
that goes away
• Then this flushing reoccurs, lasting
longer each time
• Eventually it becomes a persistent
condition
• Usually strikes between the ages of 30
to 50
Rosacea
• Sometimes associated with heavy
drinking – but not true
• Alcohol does worsen the condition, but
so does spicy foods, hot baths, and
exposure to sun
• Comedian W.C. Fields had this condition
on his nose
Port Wine Stains
• Blazing red birthmarks
– Bright pink to purple blotches on
the skin
• Some Central American countries
thought these were the mark of
the devil
• Gypsies believed they were signs of
the mother’s guilt
Port Wine Stains
• No known cause
• Happens during fetal development
• Laser therapy can remove, but is
very costly
Tattoos
• Using a needle to
deposit pigment in
the skin dermis
• Originated around
8000 BC
• Can be dangerous
– Risk of allergic reaction
and bloodborne
infectious diseases such
as hepatitis
Quiz
Appendages of the
Skin
Next time!
Complete study guide pages
106-108