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Week 13
The
Integumentary
System
The integumentary system
consists of:
• The Skin
• Its Derivatives
– Hair
– Nails
– Glands
Objective 1
Structures of the Integument
Anatomy of the Skin
video
Click on title to hyperlink website
This silent film from 1926 takes us through the basic
physiology of the human skin, combining anatomical
education and basic healthcare advice. We see the
epidermis and its replacement, the structure of the
underlying dermis, nails, sweat glands and hair
follicles.
Skin Layers
The two primary skin layers are:
Epidermis:
superficial layer made of keratinized stratified
squamous epithelium (subdivided into 4-5 layers)
Dermis:
consists of areolar tissue and dense irregular
connective tissue (subdivided into 2 layers)
Plus:
Hypodermis:
attaches skin to underlying structures; made of areolar
tissue and variable amounts of adipose
The Epidermis
Epidermis
The Epidermis is:
• The superficial layer of
the Integument
• Composed of keratinized
stratified squamous
epithelium
• Majority of cells are
called keratinocytes
• Avascular
The epidermis has either 4 or 5 cell layers
Thin skin has 4 layers;
the stratum lucidum is
absent
Thick skin of the
palms and soles of the
feet has 5 layers
Layers of the Epidermis:
Layer
Structure
Stratum corneum
20-30 rows of flat dead
keratinocytes
Stratum lucidum
2-3 rows of dead
keratinocytes, found only in
thick skin
Stratum granulosum
3-5 rows of flat
keratinocytes
Stratum spinosum
8-10 rows of flat
keratinocytes,
Stratum basale
single layer of
keratinocytes; some
melanocytes,
and Merkel cells
Number of rows are less in thin skin and more in thick skin
Thin skin
S. Corneum
S. Granulosum
S. Spinosum
S. Basale
High power magnification
Thick skin
S. Corneum
S. Lucidum
S. Granulosum
S. Spinosum
S. Basale
Low power magnification
Comparing the two together:
Pigmented Skin
How melanin granules pigment the skin:
Melanocyte cytoplams are unstained and appear white
Melanosomes (w/ melanin) are stained dark
Pigmented skin
Melanin
granules
Melanocyte
Review:
Identify each layer
? S. corneum
? S. Lucidum
? S. Granulosum
? S. Spinosum
How do you distinguish each layer?
? S. Basale
Identify as: Thin skin or Thick skin?
THIN
THICK
The Dermis
Dermal papillae
Dermis
The Dermis is:
epidermis
• Deep to the epidermis
• Composed of connective
tissue
• Consists of a superficial
papillary layer and a
deep reticular layer
• Contains sensory
receptors, nerve fibers,
glands, and hair follicles
Papillary layer
Reticular layer
dermis
Layers of the Dermis
Papillary Layer
Areolar C.T.
• Collagen fibers
• Elastic
• Reticular fibers
Reticular Layer
Dense Irregular C.T.
• Collagen fibers
Review:
Thin skin
Thick
or thin skin?
Tissue type?
Stratified
squamous
Papillarylayer?
Dermal
Tissue type?
Areolar
CT
Reticularlayer?
Dermal
Tissue Irregular
Dense
type?
Dermal papillae not normally noticeable in thin skin as in thick skin
Skin Derivatives
Hair shaft
Pore
Sebaceous (oil)
gland
Arrector pili muscle
Hair root
Hair follicle
Hair bulb
Hair papilla
Eccrine
(sweat) gland
Skin derivatives found in the dermis:
Sudoriferous (sweat) glands:
Eccrine
Apocrine
Sudoriferous (sweat) glands
Cross section
Low magnification
High magnification
Skin derivatives found in the dermis:
Arrector pili
muscle
Sebaceous (oil)
gland
Hair
Structures
HAIR STRUCTURES
Hair shaft
Sebaceous
gland
Hair root
Connective
tissue root
sheath
Epithelial
root sheath
(Hair follicle)
Hair Bulb
Hair Papilla
Arrector pili
muscle
Hair Structures
Hair Bulb
Hair Shaft
(visible hair)
Hair Root
(embedded)
Histology – Hair Structures
Hair Root
Hair
Follicle
Hair Bulb
Hair
Papilla
Histology – Hair Structures
Hair
follicle
Histology – Arrector pili muscle
(smooth muscle)
Histology – Hair Structures
Sebaceous (oil) gland
Histology – Hair Structures
Sebaceous (oil)
gland
Hair shaft
Hair root
Hair
follicle
Arrector
pili
Sebaceous
(oil) gland
Hair
Root
Hair
Follicle
Cutaneous Sensory Receptors
Meissner's corpuscle
Free nerve ending
Pacinian corpuscle
Hair follicle receptor
(root hair plexus)
The cutaneous sensory receptors are nerve endings that receive
stimuli from the external environment through the skin
(Exteroceptors)
Spinal cord
Histology
Pacinian corpuscles
Meissner’s corpuscles
Located deep in dermis
Located in dermal papilla
External
Internal
Meissner’s corpuscle - Histology
Located in the dermal papilla
Tactile receptors = Discriminative touch
Pacinian corpuscle - Histology
Located deep in the dermis
Deep pressure
High magnification
Low magnification
Review
5
6
2
1
4
3
9
8
7
10
Review
Hair shaft
6
Meissner's7corpuscle
Free nerve
8 ending
9
Sebaceous (oil)
gland
Hair1root
Hair follicle
2
Arrector 10
pili muscle
Pacinian11
corpuscle
Hair3bulb
Hair papilla
4
5
Eccrine
(sweat) gland
Root hair
12 plexus
Objective 2
General Sensation
Additional Information
Although a part of the nervous system, cutaneous receptors
have a direct impact on the integument, and so will be
studied in this lab
Consequences of Sensation Loss
Diabetic neuropathy
Nerve damage due to decreased blood flow
•Ulcers and infections - skin damage undetected
•Charcot's Joint (neuropathic arthropathy)
•Loss of motor function
Consequences of Sensation Loss
Leprosy (Hansen’s disease)
Lesions and infections from inability to detect
tissue and bone injury resulting from nerve damage
caused by the bacterium Mycobacterium leprae
Appendage loss
due to infection
Blindness and nasal
collapse also result
from nerve damage
There are 3 ways to classify cutaneous receptors:
Location ………..………….
Stimulus (physiology)
Structure (anatomy)
Classifications of Sensory Receptors
by Location
Exteroceptors
Proprioceptors
Interoceptors
Respond to stimuli arising
outside the body:
Touch
Pain
Temperature
Pressure
Detect
stretch
Respond to stimuli
inside the body
(viscera, vessels)
Classifications of Sensory Receptors
by Stimulus
Nociceptors detect pain
Thermoreceptors detect heat and cold
Mechanoreceptors detect touch and pressure
Photoreceptors detect light
These are the ones you utilized in Lab 12
Chemoreceptors detect chemicals and chemical changes
Classifications of Sensory Receptors
by Structure
Unencapsulated
Encapsulated
Connective tissue
capsule
Free Nerve Ending
Encapsulated Nerve Ending
Free (Unencapsulated) Nerve Endings
Root hair plexus
Detect hair
movement
Mechanoreceptor
Phasic
Free nerve ending
in the epidermis
Detect pain,
temperature, tissue
movements
Nociceptor (tonic)
Thermoceptor (phasic)
(Mechanoreceptor)
Encapsulated Nerve Endings
Examples
Pacinian corpuscle
Meissner’s corpuscle
Detect deep pressure,
stretch, vibration
Detect light pressure,
discriminative touch,
vibration
Mechanoreceptors
Mechanoreceptor
Phasic
Phasic
Distribution of cutaneous
sensory receptors
Functional Mapping of Somatosensory Cortex
The picture
represents the
sensory
information
covered by a
particular
portion of the
post-central
gyrus.
Consider what
impact this may
have on the
receptive fields
of the different
areas tested in
this experiment.
Adaptation: Tonic vs. Phasic
Pain
Stretch
Temperature
Pressure
Sensation
diminishes but
never ceases
Sensation ceases
(becomes
unnoticeable)
Receptive Fields and Adaptation of Select Receptors
Phasic
Tonic
Phasic
Tonic