Transcript 26 slides

MONDAY, SEPTEMBER
TH
26
This week’s agenda:
Monday – Tissue and Skin Lecture
Tuesday – Debrief skin lab and UV lab
Wednesday – Burns Case Study
Thursday – Review/Tutorials
Friday – Tissues and Skin Exam
Body Tissues
 Tissues
 Groups of cells with similar structure and function
 Four primary types:
1.
2.
3.
4.
© 2015 Pearson Education, Inc.
Epithelial tissue (epithelium)
Connective tissue
Muscle tissue
Nervous tissue
1. Epithelial Tissues!
© 2015 Pearson Education, Inc.
Epithelial Tissues
 Locations:
 Body coverings
 Body linings
 Glandular tissue
 Functions:
 Protection
 Absorption
 Filtration
 Secretion
© 2015 Pearson Education, Inc.
Epithelium Characteristics
 Cells fit closely together and often form sheets
 The apical surface is the free surface of the tissue
 The lower surface of the epithelium rests on a basement membrane
 Avascular (no blood supply)
 Regenerate easily if well nourished
© 2015 Pearson Education, Inc.
Figure 3.17a Classification and functions of epithelia.
Apical surface
Basal
surface
Simple
Apical surface
Basal
surface Stratified
(a) Classification based on number of cell layers
© 2015 Pearson Education, Inc.
Classification of Epithelia
 Shape of cells
 Squamous
 Flattened, like fish scales
 Cuboidal
 Cube-shaped, like dice
 Columnar
 Column-like
© 2015 Pearson Education, Inc.
Figure 3.17b Classification and functions of epithelia.
Squamous
Cuboidal
Columnar
(b) Classification based on cell shape
© 2015 Pearson Education, Inc.
Figure 3.17c Classification and functions of epithelia.
Number of layers
One layer: simple epithelial
tissues
More than one layer: stratified
epithelial tissues
Squamous
Diffusion and filtration
Secretion in serous membranes
Protection
Cuboidal
Secretion and absorption; ciliated
types propel mucus or
reproductive cells
Secretion and absorption; ciliated
types propel mucus or
reproductive cells
Protection; these tissue types are rare
in humans
Cell shape
Columnar
Transitional
Protection; stretching to accommodate
distension of urinary structures
(c) Function of epithelial tissue related to tissue type
© 2015 Pearson Education, Inc.
Simple Epithelia
 Simple squamous
 Single layer of flat cells
 Location—usually forms membranes
 Lines air sacs of the lungs
 Forms walls of capillaries
 Forms serous membranes (serosae) that line and cover organs in ventral
cavity
 Functions in diffusion, filtration, or secretion in membranes
© 2015 Pearson Education, Inc.
Figure 3.18a Types of epithelia and their common locations in the body.
Air sacs of
lungs
Nucleus of
squamous
epithelial cell
Basement
membrane
(a) Diagram: Simple squamous
© 2015 Pearson Education, Inc.
Nuclei of
squamous
epithelial
cells
Photomicrograph: Simple
squamous epithelium forming part
of the alveolar (air sac) walls (275×).
Simple Epithelia
 Simple cuboidal
 Single layer of cube-like cells
 Locations:
 Common in glands and their ducts
 Forms walls of kidney tubules
 Covers the surface of ovaries
 Functions in secretion and absorption; ciliated types propel mucus or
reproductive cells
© 2015 Pearson Education, Inc.
Figure 3.18b Types of epithelia and their common locations in the body.
Nucleus of
simple
cuboidal
epithelial
cell
Basement
membrane
(b) Diagram: Simple cuboidal
© 2015 Pearson Education, Inc.
Simple
cuboidal
epithelial
cells
Basement
membrane
Connective
tissue
Photomicrograph: Simple cuboidal
epithelium in kidney tubules (250×).
Simple Epithelia
 Simple columnar
 Single layer of tall cells
 Goblet cells secrete mucus
 Location:
 Lines digestive tract from stomach to anus
 Mucous membranes (mucosae) line body cavities opening to the exterior
 Functions in secretion and absorption; ciliated types propel mucus or
reproductive cells
© 2015 Pearson Education, Inc.
Figure 3.18c Types of epithelia and their common locations in the body.
Nucleus of
simple columnar
epithelial cell
Basement
membrane
(c) Diagram: Simple columnar
© 2015 Pearson Education, Inc.
Mucus of a
goblet cell
Simple
columnar
epithelial cells
Basement
membrane
Photomicrograph: Simple columnar
epithelium of the small intestine (575×).
Simple Epithelia
 Pseudostratified columnar
 All cells rest on a basement membrane
 Single layer, but some cells are shorter than others giving a false
(pseudo) impression of stratification
 Location:
 Respiratory tract, where it is ciliated and known as pseudostratified ciliated
columnar epithelium
 Functions in absorption or secretion
© 2015 Pearson Education, Inc.
Figure 3.18d Types of epithelia and their common locations in the body.
Cilia
Pseudostratified
epithelial
layer
Pseudostratified
epithelial layer
Basement
membrane
Basement
membrane
Connective
tissue
(d) Diagram: Pseudostratified
(ciliated) columnar
© 2015 Pearson Education, Inc.
Photomicrograph: Pseudostratified
ciliated columnar epithelium lining the
human trachea (560×).
Stratified Epithelia
 Stratified squamous
 Named for cells present at the free (apical) surface, which are flattened
 Functions as a protective covering where friction is common
 Locations—lining of the:
 Skin (outer portion)
 Mouth
 Esophagus
© 2015 Pearson Education, Inc.
Figure 3.18e Types of epithelia and their common locations in the body.
Nuclei
Stratified
squamous
epithelium
Basement
membrane
(e) Diagram: Stratified squamous
© 2015 Pearson Education, Inc.
Stratified
squamous
epithelium
Basement
membrane
Connective
Photomicrograph:
tissue
Stratified squamous
epithelium lining of the esophagus (140×).
Stratified Epithelia
 Stratified cuboidal—two layers of cuboidal cells; functions in protection
 Stratified columnar—surface cells are columnar, and cells underneath
vary in size and shape; functions in protection
 Stratified cuboidal and columnar
 Rare in human body
 Found mainly in ducts of large glands
© 2015 Pearson Education, Inc.
Stratified Epithelia
 Transitional epithelium
 Composed of modified stratified squamous epithelium
 Shape of cells depends upon the amount of stretching
 Functions in stretching and the ability to return to normal shape
 Locations: urinary system organs
© 2015 Pearson Education, Inc.
Figure 3.18f Types of epithelia and their common locations in the body.
Basement
membrane
Transitional
epithelium
Basement
membrane
Transitional
epithelium
Connective
tissue
(f) Diagram: Transitional
© 2015 Pearson Education, Inc.
Photomicrograph: Transitional epithelium lining of
the bladder, relaxed state (270×); surface rounded cells
flatten and elongate when the bladder fills with urine.
Glandular Epithelium
 Gland
 One or more cells responsible for secreting a particular product
 Secretions contain protein molecules in an aqueous (water-based) fluid
 Secretion is an active process
© 2015 Pearson Education, Inc.
Glandular Epithelium
 Two major gland types
 Endocrine gland
 Ductless; secretions diffuse into blood vessels
 All secretions are hormones
 Examples include thyroid, adrenals, and pituitary
© 2015 Pearson Education, Inc.
Glandular Epithelium
 Two major gland types
 Exocrine gland
 Secretions empty through ducts to the epithelial surface
 Include sweat and oil glands, liver, and pancreas
 Includes both internal and external glands
© 2015 Pearson Education, Inc.
2. Connective Tissue!
© 2015 Pearson Education, Inc.
Connective Tissue
 Found everywhere in the body
 Includes the most abundant and widely distributed tissues
 Functions:
 Provides protection
 Binds body tissues together
 Supports the body
© 2015 Pearson Education, Inc.
Connective Tissue Characteristics
 Variations in blood supply
 Some tissue types are well vascularized
 Some have a poor blood supply or are avascular
 Extracellular matrix
 Nonliving material that surrounds living cells
© 2015 Pearson Education, Inc.
Extracellular Matrix
 Two main elements
1. Ground substance—mostly water along with adhesion proteins and
polysaccharide molecules
2. Fibers
 Produced by the cells
 Three types:
1. Collagen (white) fibers
2. Elastic (yellow) fibers
3. Reticular fibers (a type of collagen)
© 2015 Pearson Education, Inc.
Connective Tissue Types
 From most rigid to softest, or most fluid:
 Bone
 Cartilage
 Dense connective tissue
 Loose connective tissue
 Blood
© 2015 Pearson Education, Inc.
Connective Tissue Types
 Bone (osseous tissue)
 Composed of:
 Osteocytes (bone cells) sitting in lacunae (cavities)
 Hard matrix of calcium salts
 Large numbers of collagen fibers
 Functions to protect and support the body
© 2015 Pearson Education, Inc.
Figure 3.19a Connective tissues and their common body locations.
Bone cells
in lacunae
Central
canal
Lacunae
Lamella
(a) Diagram: Bone
© 2015 Pearson Education, Inc.
Photomicrograph: Cross-sectional
view of ground bone (165×)
Connective Tissue Types
 Cartilage
 Less hard and more flexible than bone
 Found in only a few places in the body
 Chondrocyte (cartilage cell) is the major cell type
© 2015 Pearson Education, Inc.
Connective Tissue Types
 Hyaline cartilage
 Hyaline cartilage is the most widespread type of cartilage
 Composed of abundant collagen fibers and a rubbery matrix
 Locations:
 Larynx
 Entire fetal skeleton prior to birth
 Epiphyseal plates
 Functions as a more flexible skeletal element than bone
© 2015 Pearson Education, Inc.
Figure 3.19b Connective tissues and their common body locations.
Chondrocyte
(cartilage cell)
Chondrocyte
in lacuna
Lacunae
Matrix
(b) Diagram: Hyaline
cartilage
© 2015 Pearson Education, Inc.
Photomicrograph: Hyaline cartilage
from the trachea (400×)
Connective Tissue Types
 Elastic cartilage (not pictured)
 Provides elasticity
 Location:
 Supports the external ear
 Fibrocartilage
 Highly compressible
 Location:
 Forms cushionlike discs between vertebrae of the spinal column
© 2015 Pearson Education, Inc.
Figure 3.19c Connective tissues and their common body locations.
Chondrocytes
in lacunae
Chondrocytes in
lacunae
Collagen
fibers
© 2015 Pearson Education, Inc.
Collagen fiber
(c) Diagram:
Fibrocartilage
Photomicrograph: Fibrocartilage of an
intervertebral disc (150×)
Connective Tissue Types
 Dense connective tissue (dense fibrous tissue)
 Main matrix element is collagen fiber
 Fibroblasts are cells that make fibers
 Locations:
 Tendons—attach skeletal muscle to bone
 Ligaments—attach bone to bone at joints and are more elastic than
tendons
 Dermis—lower layers of the skin
© 2015 Pearson Education, Inc.
Figure 3.19d Connective tissues and their common body locations.
Ligament
Tendon
Collagen
fibers
Collagen
fibers
Nuclei of
fibroblasts
Nuclei of
fibroblasts
(d) Diagram: Dense
fibrous
© 2015 Pearson Education, Inc.
Photomicrograph: Dense fibrous
connective tissue from a tendon (475×)
Connective Tissue Types
 Loose connective tissue types
 Areolar tissue
 Most widely distributed connective tissue
 Soft, pliable tissue like “cobwebs”
 Functions as a universal packing tissue and “glue” to hold organs in place
 Layer of areolar tissue called lamina propria underlies all membranes
 All fiber types form a loose network
 Can soak up excess fluid (causes edema)
© 2015 Pearson Education, Inc.
Figure 3.19e Connective tissues and their common body locations.
Mucosa
epithelium
Lamina
propria
Elastic
fibers
Collagen
fibers
Fibroblast
nuclei
Fibers of
matrix
Nuclei of
fibroblasts
(e) Diagram: Areolar
© 2015 Pearson Education, Inc.
Photomicrograph: Areolar connective tissue,
a soft packaging tissue of the body (270×)
Connective Tissue Types
 Loose connective tissue types
 Adipose tissue
 Matrix is an areolar tissue in which fat globules predominate
 Many cells contain large lipid deposits with nucleus to one side (signet ring
cells)
 Functions
 Insulates the body
 Protects some organs
 Serves as a site of fuel storage
© 2015 Pearson Education, Inc.
Figure 3.19f Connective tissues and their common body locations.
Nuclei of
fat cells
Vacuole
containing
fat droplet
Nuclei of
fat cells
Vacuole
containing
fat droplet
(f) Diagram: Adipose
© 2015 Pearson Education, Inc.
Photomicrograph: Adipose tissue from the
subcutaneous layer beneath the skin (570×)
Connective Tissue Types
 Loose connective tissue types
 Reticular connective tissue
 Delicate network of interwoven fibers with reticular cells (like fibroblasts)
 Locations:
 Forms stroma (internal framework) of organs, such as these lymphoid organs:
 Lymph nodes
 Spleen
 Bone marrow
© 2015 Pearson Education, Inc.
Figure 3.19g Connective tissues and their common body locations.
Spleen
White blood cell
(lymphocyte)
Reticular
cell
Blood
cell
Reticular
fibers
Reticular fibers
(g) Diagram: Reticular
© 2015 Pearson Education, Inc.
Photomicrograph: Dark-staining network
of reticular connective tissue (400×)
Connective Tissue Types
 Blood (vascular tissue)
 Blood cells surrounded by fluid matrix known as blood plasma
 Soluble fibers are visible only during clotting
 Functions as the transport vehicle for the cardiovascular system,
carrying:
 Nutrients
 Wastes
 Respiratory gases
© 2015 Pearson Education, Inc.
Figure 3.19h Connective tissues and their common body locations.
Blood cells
in capillary
Neutrophil
(white blood
cell)
Red blood
cells
White
blood cell
Red
blood cells
(h) Diagram: Blood
© 2015 Pearson Education, Inc.
Monocyte
(white blood
cell)
Photomicrograph: Smear of human
blood (1290×)
3. Muscular Tissue!
Muscle Tissue
 Function is to contract, or shorten, to produce movement
 Three types:
1. Skeletal muscle
2. Cardiac muscle
3. Smooth muscle
© 2015 Pearson Education, Inc.
Muscle Tissue Types
 Skeletal muscle
 Voluntarily (consciously) controlled
 Attached to the skeleton and pull on bones or skin
 Produces gross body movements or facial expressions
 Characteristics of skeletal muscle cells
 Striations (stripes)
 Multinucleate (more than one nucleus)
 Long, cylindrical shape
© 2015 Pearson Education, Inc.
Figure 3.20a Type of muscle tissue and their common locations in the body.
Nuclei
Part of muscle
fiber
(a) Diagram: Skeletal muscle
© 2015 Pearson Education, Inc.
Photomicrograph: Skeletal muscle (195×)
Muscle Tissue Types
 Cardiac muscle
 Involuntarily controlled
 Found only in the heart
 Pumps blood through blood vessels
 Characteristics of cardiac muscle cells
 Striations
 Uninucleate, short, branching cells
 Intercalated discs contain gap junctions to connect cells together
© 2015 Pearson Education, Inc.
Figure 3.20b Type of muscle tissue and their common locations in the body.
Intercalated
discs
Nucleus
(b) Diagram: Cardiac muscle
© 2015 Pearson Education, Inc.
Photomicrograph: Cardiac muscle (475×)
Muscle Tissue Types
 Smooth (visceral) muscle
 Involuntarily controlled
 Found in walls of hollow organs such as stomach, uterus, and blood
vessels
 Peristalsis, a wavelike activity, is a typical activity
 Characteristics of smooth muscle cells
 No visible striations
 Uninucleate
 Spindle-shaped cells
© 2015 Pearson Education, Inc.
Figure 3.20c Type of muscle tissue and their common locations in the body.
Smooth
muscle cell
Nuclei
(c) Diagram: Smooth muscle
© 2015 Pearson Education, Inc.
Photomicrograph: Sheet of smooth muscle (285×)
3. Nervous Tissue!
© 2015 Pearson Education, Inc.
Nervous Tissue
 Composed of neurons and nerve support cells
 Function is to receive and conduct electrochemical impulses to and
from body parts
 Irritability
 Conductivity
 Support cells called neuroglia insulate, protect, and support neurons
© 2015 Pearson Education, Inc.
Figure 3.21 Nervous tissue.
Brain
Nuclei of
supporting
cells
Spinal
cord
Nuclei of
supporting
cells
Cell body
of neuron
Neuron
processes
© 2015 Pearson Education, Inc.
Cell body
of neuron
Neuron
processes
Diagram: Nervous
tissue
Photomicrograph: Neurons (320×)
Figure 3.22 Summary of the major functions and body locations of the four tissue types: epithelial, connective, muscle, and nervous tissues.
Nervous tissue: Internal communication
• Brain, spinal cord, and nerves
Muscle tissue: Contracts to cause movement
• Muscles attached to bones (skeletal)
• Muscles of heart (cardiac)
• Muscles of walls of hollow organs (smooth)
Epithelial tissue: Forms boundaries between
different environments, protects, secretes, absorbs,
filters
• Lining of GI tract organs and other hollow organs
• Skin surface (epidermis)
Connective tissue: Supports, protects, binds
other tissues together
• Bones
• Tendons
• Fat and other soft padding tissue
© 2015 Pearson Education, Inc.
Tissue Repair!
Tissue Repair (Wound Healing)
 Tissue repair (wound healing) occurs in two ways:
1. Regeneration
 Replacement of destroyed tissue by the same kind of cells
2. Fibrosis
 Repair by dense (fibrous) connective tissue (scar tissue)
© 2015 Pearson Education, Inc.
Tissue Repair (Wound Healing)
 Whether regeneration or fibrosis occurs depends on:
1. Type of tissue damaged
2. Severity of the injury
 Clean cuts (incisions) heal more successfully than ragged tears of the
tissue
© 2015 Pearson Education, Inc.
Events in Tissue Repair
 Inflammation
 Capillaries become very permeable
 Clotting proteins migrate into the area from the bloodstream
 A clot walls off the injured area
 Granulation tissue forms
 Growth of new capillaries
 Phagocytes dispose of blood clot and fibroblasts
 Rebuild collagen fibers
© 2015 Pearson Education, Inc.
Events in Tissue Repair
 Regeneration of surface epithelium
 Scab detaches
 Whether scar is visible or invisible depends on severity of wound
© 2015 Pearson Education, Inc.
Regeneration of Tissues
 Tissues that regenerate easily
 Epithelial tissue (skin and mucous membranes)
 Fibrous connective tissues and bone
 Tissues that regenerate poorly
 Skeletal muscle
 Tissues that are replaced largely with scar tissue
 Cardiac muscle
 Nervous tissue within the brain and spinal cord
© 2015 Pearson Education, Inc.
Tissue Development!
© 2015 Pearson Education, Inc.
Development Aspects of Cells and Tissues
 Growth through cell division continues through puberty
 Cell populations exposed to friction (such as epithelium) replace lost
cells throughout life
 Connective tissue remains mitotic and forms repair (scar) tissue
 With some exceptions, muscle tissue becomes amitotic by the end of
puberty
 Nervous tissue becomes amitotic shortly after birth.
© 2015 Pearson Education, Inc.
Developmental Aspects of Cells and Tissues
 Injury can severely handicap amitotic tissues
 The cause of aging is unknown, but chemical and physical insults, as
well as genetic programming, have been proposed as possible causes
© 2015 Pearson Education, Inc.
Developmental Aspects of Cells and Tissues
 Neoplasms, both benign and cancerous, represent abnormal cell
masses in which normal controls on cell division are not working
 Hyperplasia (increase in size) of a tissue or organ may occur when
tissue is strongly stimulated or irritated
 Atrophy (decrease in size) of a tissue or organ occurs when the organ
is no longer stimulated normally
© 2015 Pearson Education, Inc.
Membranes!
© 2015 Pearson Education, Inc.
Body Membranes
 Functions of body membranes
 Cover body surfaces
 Line body cavities
 Form protective sheets around organs
 Classified according to tissue types
© 2015 Pearson Education, Inc.
Classification of Body Membranes
 Epithelial membranes
 Cutaneous membranes
 Mucous membranes
 Serous membranes
 Connective tissue membranes
 Synovial membranes
© 2015 Pearson Education, Inc.
Cutaneous Membrane
 Cutaneous membrane  skin
 Dry membrane
 Outermost protective boundary
 Superficial epidermis is composed of keratinized stratified squamous
epithelium
 Underlying dermis is mostly dense (fibrous)
connective tissue
© 2015 Pearson Education, Inc.
Figure 4.1a Classes of epithelial membranes.
Cutaneous
membrane
(skin)
(a) Cutaneous membrane
(the skin) covers the
body surface.
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
 Moist membranes adapted for absorption or secretion
© 2015 Pearson Education, Inc.
Figure 4.1b Classes of epithelial membranes.
Mucosa of
nasal cavity
Mucosa of
mouth
Esophagus
lining
Mucosa of
lung bronchi
(b) Mucous membranes line body
cavities open to the exterior.
Serous Membranes (Serosa)
 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
© 2015 Pearson Education, Inc.
Figure 4.1d Classes of epithelial membranes.
Outer balloon wall
(comparable to
parietal serosa)
Air (comparable to
serous cavity)
Inner balloon wall
(comparable to
visceral serosa)
(d) A fist thrust into a flaccid
balloon demonstrates the
relationship between the
parietal and visceral
serous membrane layers.
Serous Membranes
 Specific serous membranes
 Peritoneum
 Abdominal cavity
 Pleura
 Around the lungs
 Pericardium
 Around the heart
© 2015 Pearson Education, Inc.
Figure 4.1c Classes of epithelial membranes.
Parietal
pleura
Visceral
pleura
Parietal
peritoneum
Visceral
peritoneum
Parietal
pericardium
Visceral
pericardium
(c) Serous membranes line body
cavities closed to the exterior.
Connective Tissue Membrane
 Synovial membrane
 Connective tissue only
 Lines fibrous capsules surrounding joints
 Lines bursae
 Lines tendon sheaths
 Secretes a lubricating fluid
© 2015 Pearson Education, Inc.
Figure 4.2 A typical synovial joint.
Ligament
Joint cavity
(contains
synovial fluid)
Articular (hyaline)
cartilage
Fibrous
layer
Articular
Synovial
capsule
membrane
Integumentary System!
Integumentary System
 Integumentary system includes:
 Skin (cutaneous membrane)
 Skin derivatives
 Sweat glands
 Oil glands
 Hair
 Nails
© 2015 Pearson Education, Inc.
Skin (Integument) Functions
 Protects deeper tissues from:
 Mechanical damage (bumps)
 Chemical damage (acids and bases)
 Bacterial damage
 Ultraviolet radiation (sunlight)
 Thermal damage (heat or cold)
 Desiccation (drying out)
 Keratin protects the skin from water loss
© 2015 Pearson Education, Inc.
Skin Functions
 Aids in loss or retention of body heat as controlled by the nervous
system
 Aids in excretion of urea and uric acid
 Synthesizes vitamin D
 Cutaneous sensory receptors detect touch, temperature, pressure,
and pain
© 2015 Pearson Education, Inc.
Table 4.1 Functions of the Integumentary System (1 of 2).
Table 4.1 Functions of the Integumentary System (2 of 2).
Skin Structure
 Epidermis—outer layer
 Stratified squamous epithelium
 Cornified or keratinized (hardened by keratin) to prevent water loss
 Avascular
 Most cells are keratinocytes
 Dermis
 Dense connective tissue
© 2015 Pearson Education, Inc.
Figure 4.3 Skin structure.
Hair shaft
Dermal papillae
Epidermis
Papillary
layer
Dermis
Pore
Appendages of skin
• Eccrine sweat gland
• Arrector pili muscle
• Sebaceous (oil) gland
• Hair follicle
• Hair root
Reticular
layer
Hypodermis
(subcutaneous
tissue)
Nervous structures
• Sensory nerve fiber
• Lamellar corpuscle
• Hair follicle receptor
(root hair plexus)
Cutaneous vascular plexus
Adipose tissue
Skin Structure
 Subcutaneous tissue (hypodermis) is deep to dermis
 Not technically part of the skin
 Anchors skin to underlying organs
 Composed mostly of adipose tissue
 Serves as a shock absorber and insulates deeper tissues
© 2015 Pearson Education, Inc.
Layers of the Epidermis
 The epidermis is composed of up to five layers
 The epidermis is avascular
 Most of the cells in the epidermis are keratinocytes
 Keratin, a fibrous protein, makes the epidermis tough
 The layers are covered, next, from deepest to most superficial
© 2015 Pearson Education, Inc.
Dermis
 Two layers:
1. Papillary layer (upper dermal region)
 Projections called dermal papillae
 Some contain capillary loops
 Others house pain receptors (free nerve endings) and touch receptors
 Fingerprints are identifying films of sweat
2. Reticular layer (deepest skin layer)
 Blood vessels
 Sweat and oil glands
 Deep pressure receptors (lamellar corpuscles)
© 2015 Pearson Education, Inc.
Dermis
 Overall dermis structure
 Collagen and elastic fibers located throughout the dermis
 Collagen fibers give skin its toughness
 Elastic fibers give skin elasticity
 Blood vessels play a role in body temperature regulation
 Nerve supply sends messages to the central nervous system
© 2015 Pearson Education, Inc.
Figure 4.5 Light micrograph of the two regions of the dermis (100×).
Epidermis
Papillary
layer
Dermis
Reticular
layer
Skin Color
 Three pigments contribute to skin color:
1. Melanin
 Yellow, reddish brown, or black pigments
2. Carotene
 Orange-yellow pigment from some vegetables
3. Hemoglobin
 Red coloring from blood cells in dermal capillaries
 Oxygen content determines the extent of red coloring
© 2015 Pearson Education, Inc.
Melanin
 Pigment (melanin) produced by melanocytes
 Color is yellow to brown to black
 Melanocytes are mostly in the stratum basale
 Melanin accumulates in membrane-bound granules called
melanosomes
 Amount of melanin produced depends upon genetics and exposure to
sunlight
© 2015 Pearson Education, Inc.
Alterations in Skin Color
 Redness (erythema)—due to embarrassment, inflammation,
hypertension, fever, or allergy
 Pallor (blanching)—due to emotional stress (such as fear), anemia,
low blood pressure, impaired blood flow to an area
 Jaundice (yellowing)—liver disorder
 Bruises (black and blue marks)—hematomas
© 2015 Pearson Education, Inc.
Appendages of the Skin
 Cutaneous glands are all exocrine glands
 Sebaceous glands
 Sweat glands
 Hair
 Hair follicles
 Nails
© 2015 Pearson Education, Inc.
Figure 4.3 Skin structure.
Hair shaft
Dermal papillae
Epidermis
Papillary
layer
Dermis
Pore
Appendages of skin
• Eccrine sweat gland
• Arrector pili muscle
• Sebaceous (oil) gland
• Hair follicle
• Hair root
Reticular
layer
Hypodermis
(subcutaneous
tissue)
Nervous structures
• Sensory nerve fiber
• Lamellar corpuscle
• Hair follicle receptor
(root hair plexus)
Cutaneous vascular plexus
Adipose tissue
Appendages of the Skin
 Sebaceous (oil) glands
 Produce sebum (oil)
 Lubricant for skin
 Prevents brittle hair
 Kills bacteria
 Most have ducts that empty into hair follicles; others open directly onto
skin surface
 Glands are activated at puberty
© 2015 Pearson Education, Inc.
Figure 4.7a Cutaneous glands.
Sweat
pore
Eccrine
gland
Sebaceous
gland
Sebaceous
gland duct
Dermal connective
tissue
Hair in
hair follicle
Secretory cells
(a) Photomicrograph of a sectioned
sebaceous gland (100×)
Appendages of the Skin
 Sweat (sudoriferous) glands
 Produce sweat
 Widely distributed in skin
© 2015 Pearson Education, Inc.
Appendages of the Skin
 Two types of sudoriferous glands
1. Eccrine glands
 Open via duct to pore on skin surface
 Produce sweat
© 2015 Pearson Education, Inc.
Appendages of the Skin
 Sweat:
 Composition
 Mostly water
 Salts and vitamin C
 Some metabolic waste
 Fatty acids and proteins (apocrine only)
 Function
 Helps dissipate excess heat
 Excretes waste products
 Acidic nature inhibits bacteria growth
 Odor is from associated bacteria
© 2015 Pearson Education, Inc.
Figure 4.7b Cutaneous glands.
Sweat
pore
Eccrine
gland
Sebaceous
gland
Dermal connective
tissue
Eccrine
gland duct
Secretory cells
(b) Photomicrograph of a sectioned
eccrine gland (205×)
Appendages of the Skin
 Two types of sudoriferous glands
2. Apocrine glands
 Ducts empty into hair follicles
 Begin to function at puberty
 Release sweat that also contains fatty acids and proteins (milky or
yellowish color)
© 2015 Pearson Education, Inc.
Appendages of the Skin
 Hair
 Produced by hair follicle
 Root is enclosed in the follicle
 Shaft projects from the surface of the scalp or skin
 Consists of hard keratinized epithelial cells
 Melanocytes provide pigment for hair color
 Hair grows in the matrix of the hair bulb in stratum basale
© 2015 Pearson Education, Inc.
Appendages of the Skin
 Associated hair structures
 Hair follicle
 Dermal and epidermal sheath surround hair root
 Arrector pili muscle
 Smooth muscle
 Pulls hairs upright when person is cold or frightened
 Sebaceous gland
 Sudoriferous gland
© 2015 Pearson Education, Inc.
Figure 4.10 Structure of a nail.
Lunule
Lateral
nail fold
(a)
Free
edge
of
nail
(b)
Body Cuticle Root of nail
of
Proximal Nail
nail
nail fold matrix
Nail bed Bone of fingertip
Burns!
Skin Homeostatic Imbalances
 Burns
 Tissue damage and cell death caused by heat, electricity, UV radiation,
or chemicals
 Associated dangers
 Dehydration
 Electrolyte imbalance
 Circulatory shock
 Result in loss of body fluids and invasion of bacteria
© 2015 Pearson Education, Inc.
Rule of Nines
 Way to determine the extent of burns
 Body is divided into 11 areas for quick estimation
 Each area represents about 9 percent of total body surface area
 The area surrounding the genitals (the perineum) represents 1 percent
of body surface area
© 2015 Pearson Education, Inc.
Figure 4.11a Burns.
Totals
Anterior and posterior
head and neck, 9%
41/2%
Anterior and posterior
upper limbs, 18%
Anterior and posterior
41/2% trunk, 36%
41/2%
Anterior
trunk, 18%
Perineum, 1%
9% 9%
Anterior and posterior
lower limbs, 36%
100%
(a)
Severity of Burns
 First-degree burns (partial-thickness burn)
 Only epidermis is damaged
 Skin is red and swollen
 Second-degree burns (partial-thickness burn)
 Epidermis and upper dermis are damaged
 Skin is red with blisters
 Third-degree burns (full-thickness burn)
 Destroys entire skin layer; burned area is painless
 Requires skin grafts
 Burn is gray-white or black
© 2015 Pearson Education, Inc.
Figure 4.11b Burns.
Burns of increasing
severity, from top to
bottom: first-degree,
second-degree,
third-degree.
(b)
Critical Burns
 Burns are considered critical if
 Over 25 percent of body has second-degree burns
 Over 10 percent of the body has third-degree burns
 There are third-degree burns of the face, hands, or feet
© 2015 Pearson Education, Inc.
Homeostatic Imbalances!
© 2015 Pearson Education, Inc.
Skin Homeostatic Imbalances
 Infections
 Athlete’s foot (tinea pedis)
 Caused by fungal infection
 Boils and carbuncles
 Caused by bacterial infection
 Cold sores
 Caused by virus
© 2015 Pearson Education, Inc.
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
© 2015 Pearson Education, Inc.
Figure 4.12 Cutaneous lesions.
(a) Cold sores
(b) Impetigo
(c) Psoriasis
Skin Cancer
 Cancer—abnormal cell mass
 Classified two ways
1. Benign
 Does not spread (encapsulated)
2. Malignant
 Metastasizes (moves) to other parts of the body
 Skin cancer is the most common type of cancer
© 2015 Pearson Education, Inc.
© 2015 Pearson Education, Inc.
Skin Cancer Types
 Basal cell carcinoma
 Least malignant
 Most common type
 Arises from stratum basale
© 2015 Pearson Education, Inc.
Figure 4.13a Photographs of skin cancers.
(a) Basal cell carcinoma
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
© 2015 Pearson Education, Inc.
Figure 4.13b Photographs of skin cancers.
(b) Squamous cell
carcinoma
Skin Cancer Types
 Malignant melanoma
 Most deadly of skin cancers
 Cancer of melanocytes
 Metastasizes rapidly to lymph and blood vessels
 Detection uses ABCD rule
© 2015 Pearson Education, Inc.
ABCD Rule
 A  Asymmetry
 Two sides of pigmented mole do not match
 B  Border irregularity
 Borders of mole are not smooth
 C  Color
 Different colors in pigmented area
 D  Diameter
 Spot is larger than 6 mm in diameter
 E = Evolving
 Changing over time, especially after age 18
© 2015 Pearson Education, Inc.
Figure 4.13c Photographs of skin cancers.
(c) Melanoma
Developmental Aspects of Skin
 In youth, skin is thick, resilient, and well hydrated
 With aging, skin loses elasticity and thins
 Skin cancer is a major threat to skin exposed to excessive sunlight
 Balding and/or graying occurs with aging; both are genetically
determined; other factors that may contribute include drugs and
emotional stress
© 2015 Pearson Education, Inc.
HOMEWORK
Make sure all of your assignments are up to date! Thursday is
the last day to get any homework checked off, but the sooner
the better!
This week
Tuesday – Debrief skin lab and UV lab
Wednesday – Burns Case Study
Thursday – Review/Tutorials
Friday – Tissues and Skin Exam