Human Anatomy and Physiology
Types of Membranes
Membranes
Synovial
lines joints;
made of CT
Serous
lines body cavities that lack openings
to the outside; reduce friction
Mucous
lines cavities and tubes that
open to the outside of the body
Cutaneous
organ of the integumentary
system; aka skin
Body Membranes

Function of body membranes
 Cover body surfaces
 Line body cavities
 Form protective sheets around organs
Classification of Body
Membranes

Epithelial membranes
 Cutaneous membranes
 Mucous membranes
 Serous membranes

Connective Tissue membranes
 Synovial membranes
Cutaneous Membrane

Cutaneous membrane = skin
 Dry membrane
 Outermost protective boundary
Superficial epidermis is composed of
keratinized stratified squamous
epithelium
 Underlying dermis is mostly dense
connective tissue

Cutaneous Membranes
The Skin
Mucous Membranes

Surface epithelium type depends on site
 Stratified squamous epithelium (mouth,
esophagus)
 Simple columnar epithelium (rest of digestive
tract)
Underlying loose connective tissue (lamina
propria)
 Lines all body cavities that open to the
exterior body surface
 Often adapted for absorption or secretion

Mucous Membranes
Figure 4.1b
Serous Membranes
Surface is a layer of simple squamous
epithelium
 Underlying layer is a thin layer of areolar
connective tissue
 Lines open body cavities that are closed to
the exterior of the body
 Serous membranes occur in pairs
separated by serous fluid

 Visceral layer covers the outside of the organ
 Parietal layer lines a portion of the wall of
ventral body cavity
Serous Membranes
Figure 4.1d
Serous Membranes

Specific serous membranes
 Peritoneum
○ Abdominal cavity
 Pleura
○ Around the lungs
 Pericardium
○ Around the heart
Serous Membranes
Figure 4.1c
Connective Tissue Membrane

Synovial membrane
 Connective tissue only
 Lines fibrous capsules
surrounding joints
 Secretes a lubricating
fluid
The Integumentary System
Functions of the Integumentary
System

Protective covering

 Prevents harmful
substances and
organisms from
entering the body
 Reduces water loss
from deeper tissues


Regulation of body
temperature
Makes up 7% of
body weight




Houses cutaneous
sensory receptors
Contains immune
system cells
Synthesizes vitamin D
Excretes small
quantities of waste
Absorption of drugs
and other agents
• Warm blood goes
through the
hypothalamus part of the
brain that regulates body
temperature  signals
muscles of dermal blood
vessels to
open(vasodilatation)
more heat escapes
through the skin
• At the same time
vasoconstriction
(narrowing) of deeper
blood vessels forces
blood to go to the
surface=skin reddens
Components of the
Integumentary System
Skin
 Hair
 Nails
 Sebaceous glands
 Sweat glands

Layers of the Skin
Epidermis
 Dermis
 Subcutaneous layer
(hypodermis)

 Hypo=under
 Dermis=skin
Thick versus Thin Skin

Thick Skin

 Found everywhere else
 Palms of hands and
soles of feet
 Hairless
 Subject to much
abrasion
 Thicker epidermis
(has an extra layer)
Thin Skin
on the body
 Has hair
 Lacks one layer of the
epidermis

“Thick” and “thin” are
not describing actual
depth of tissue!!!
 Thickest skin = upper
back
 Thinnest skin = eyelids
Thick vs. Thin Skin

Thick Skin

Thin Skin
Epidermis (epi=above)
Outer layer of skin
 Stratified squamous
epithelium
 Lacks blood vessels

 (avascular)
Grows from the
bottom layer
(stratum basale)
 Keratinizationhardening of skin

Layers of Epidermis

Stratum corneum
 TOP layer
Stratum lucidum
 Stratum granulosum
 Stratum spinosum
 Stratum basale
BOTTOM layer

 (Basement membrane)
Epidermal Layers

Stratum corneum – Keratinized stratified
squamous epithelium (which means—
hardened, layered flat cells)





Most outward layer of the epidermis
Water barrier
Varies in thickness
Thickens with unusual amounts of friction 
calluses
Stratum lucidum – in thick skin only,
cells in process of keratinization
Epidermal Layers continued…

Stratum granulosum – only a few cells
thick, appears granular
 Cells contain numerous keratin granules
Stratum spinosum – several cells thick,
numerous
 Stratum basale – single layer of cells on
bottom, contains skin stem cells

 Deepest layer of epidermis
 Cells appear cuboidal or low columnar
 Cells undergoing mitosis
Dermis







2nd LAYER OF SKIN
Epidermal ridges and dermal
papillae
Made mostly of connective
tissue
Thicker than epidermis
Muscle and nerve fibers,
blood vessels, hair follicles,
sebaceous glands, and sweat
glands
2 layers: papillary and
reticular
This layer give skin its
strength
Fingerprints form in the
Dermis during fetal
development
Layers of Dermis

Papillary layer

Reticular layer
 Thinner, superficial
 Varies in thickness,
layer
 Loose Connective
Tissue
 Contains blood
vessels that serve the
epidermis
 Contains nerve
processes
but generally thicker
than papillary layer
 Contains thicker
collagen and elastic
fibers
 May contain smooth
muscle cells
Subcutaneous Layer/Hypodermis
Not part of the skin
Loose connective
tissue and adipose
tissue
 Connective tissue
fibers are continuous
with dermis
 layer of adipose
tissue that insulates
and stores energy
 Arrector pili (goose
bumps) muscles
originate here


Cells of the Epidermis

Keratinocytes
 Main cell type
 Produce keratin (fibrous protein
that protects & toughens skin)

Melanocytes
 In stratum basale
 Produce melanin (gives skin
color)

Langerhans cells
 Help fight infection

Merkel cells
 In stratum basale
 Most abundant in fingertips
 Sense light touch
Skin Color




There are 3 pigments involved
in skin color: melanin,
carotene, and hemoglobin.
Melanin is the only pigment
made by the skin (from
tyrosine) and ranges in color
from yellow  red-brown 
black.
Skin color differences result
from the kind and amount of
melanin made and retained by
the skin cells.
All humans have relatively the
same number of Melanocytes.
Skin Color continued…
Freckles and moles are local
accumulations of melanin.
 A tan is darkening of the skin
as a result of increased
melanin production, usually in
response to prolonged
exposure to UV radiation.
 Carotene is a yelloworange
pigment found in certain plant
products. It tends to
accumulate in the stratum
corneum and in the fat of the
hypodermis, and it is more
obvious when large amounts of
carotene-rich foods are eaten.

Skin Color continued…
Hemoglobin gives a pinkish hue to fair skin
which is most noticeable in Caucasian skin.
A more crimson pigment results when the
hemoglobin is highly oxygenated.
Hemoglobin is found in the red blood cells of
the dermal capillaries.
 Hair color is genetically determined and
results from the amount and type of pigment
secreted by melanocytes near hair follicles.


Dark hair has more melanin
than light hair. Red hair
contains an iron pigment
called trichosiderin, and gray
hair is a mixture of
pigmented and unpigmented
hair.
Skin Color Continue…

Albinism-condition where a person lacks the
enzyme to make melanin (absence of skin,
hair and eye color)

Cyanosis- bluing of skin (lack of oxygen)

Jaundice- yellowing of skin (liver failure or
inability of liver to breakdown Bilirubin)

Photosensitivity- sensitivity to light (especially
when on antibiotics)
Nerve Supply to the Skin
Free nerve endings found in the
epidermis and papillary dermis
sense temperature, vibration,
pain, etc.
 Cutaneous Sensation endings:

 Pacinian corpuscles – deep dermis
and hypodermis; sense deep
pressure
 Meissner’s corpuscles – in papillary
region of dermis; sense light touch
Hair







Present on all surfaces
except for palms, soles,
lips, nipples, and parts
of external reproductive
organs
Made of keratinized
cells
Hair follicle
Hair papilla
Hair shaft
Hair color
Arrector pili
Nails






Modified epidermis
Protective coverings on
the ends of fingers and
toes
Composed mostly of
keratin
Nail plate
Nail bed
Lunula
Sebaceous Glands





Sebaceous glands are
associated with hair
follicles
Makes Oil
Sebum
Found everywhere
except palms and soles
Acne
Sweat Glands
You have over 2.5 million sweat
glands
 In dermis or superficial
subcutaneous layer
 Eccrine glands

 Most numerous
 Produce sweat on hot days and
during exercise

Apocrine glands
 Become active at puberty
 Secretions smell because of
bacterial activity
 Active during emotional upset,
fright, pain, sexual arousal


Ceruminous glands-makes
ear wax
mammary glands-makes milk
Skin Homeostatic
Imbalances

Infections
 Athlete’s foot (tinea pedis)
○ Caused by fungal infection
 Boils and carbuncles
○ Caused by bacterial infection
 Cold sores
○ Caused by herpes virus
Skin Homeostatic
Imbalances

Infections and allergies
 Contact dermatitis
○ Exposures cause allergic
reaction
 Impetigo
○ Caused by bacterial infection
 Psoriasis
○ Cause is unknown
○ Triggered by trauma,
infection, stress
Healing of Wounds
Inflammation =
normal response to
injury or stress
 Epidermal cuts
 Deep cuts

 Blood clots
 Scabs
 Scars
Healing of Burns

First degree
burns
 Superficial partial-
thickness burn

Second degree
burns
 Deep partial-
thickness burn

Third degree
burns
 Full-thickness burn


Rule of 9s
Skin graft
Dangers of severe burns

Severe burns can lead to:
 Infection (1st layer of protection is gone)
 Dehydration (water proof barrier is
broken)
 Hypothermia (insulation has been
removed)
 Scarring
 Breathing Problems
Video
Skin Cancer
Cancer—abnormal cell mass
(undergoes quick mitosis)
 Classified two ways

 Benign
○ Does not spread (encapsulated)
 Malignant
○ Metastasized (moves) to other parts of the
body

Skin cancer is the most common type of
cancer
Skin Cancer Types

Basal cell carcinoma
 Least malignant
 Most common type
 Arises from stratum basale
Skin Cancer Types

Squamous cell carcinoma
 Metastasizes to lymph nodes if not removed
 Early removal allows a good chance of cure
 Believed to be sun-induced
 Arises from stratum spinosum
Skin Cancer Types

Malignant melanoma
 Most deadly of skin cancers
 Cancer of melanocytes
 Metastasizes rapidly to lymph
and blood vessels
 Detection uses ABCDE rule
○ Asymmetry
○ Border
○ Color
○ Diameter
○ Evolution
Melanoma
(3:12)
Aging and Skin
Epidermal cells reproduce slower  larger and
more irregular shape
 Age spots – sites of oxidation of fats in secretory
cells of apocrine and eccrine glands
 Dermis reduces  wrinkling and sagging

Drier skin because of less
oil from sebaceous glands
 Gray or white hair from
decreased melanin
production

Aging – continued…





Slower hair growth and fewer hair
follicles  thinner hair and/or hair loss
Less blood supply to nail beds 
impaired growth
Diminished sensitivity to pain and
pressure because of fewer receptors
Fewer sweat glands, fewer dermal blood
vessels, and declined ability to shiver 
decreased ability to control temperature
Diminished ability to activate vitamin D
 reduced skeletal health
Ways to artificially fight aging in
Skin
Face lifts
 Tummy tucks
 Botox
 Liposuction
