Transcript CHAPTER 5: The Integumentary System

Chapter 5:
The Integumentary System
BIO 210 Lab
Instructor: Dr. Rebecca Clarke
Parts of the Integumentary System
 Cutaneous membrane (integument, skin)
 (outer) epidermis = superficial epithelium
 (inner) dermis = underlying area of connective tissues
 Accessory structures – located primarily in dermis,
protrude through epidermis to skin surface
 Hair
 Nails
 (Multicellular) exocrine glands
 Also
 Blood vessels throughout dermis
 Sensory receptors – monitor touch, pressure,
temperature, pain
Integumentary System
 Cutaneous membrane = epidermis + dermis
Figure 5–1
Layers (Strata) of Epidermis
 From basal lamina to free surface:
 stratum germinativum
 stratum spinosum
 stratum granulosum
 stratum lucidum
 stratum corneum
Stratum Germinativum (Basale)
 Single layer of basal (germinative, stem) cells
 Site of cell division; replenishes epidermis
 Attached to basal lamina by hemidesmosomes
 Forms strong bond between epidermis and dermis
Stratum Germinativum
 Forms epidermal ridges (Fig 5-2)
 fingerlike projections into dermis underneath; intermesh with
dermal papillae
  ridge-shaped pattern (fingerprint) on surface of skin which
is unique for each individual (genetically determined) (Fig 5-4)
 increase strength and bond between epidermis and dermis
 Has melanocytes (with melanin pigment) – give skin its
color (Fig 5-5)
Organization of the Epidermis
Figure 5–2
Ridges and Ducts
Figure 5–4
Stratum Spinosum
 “Spiny layer”
 cells shrink until cytoskeletons stick out (spiny)
 8-10 cell layers of keratinocytes
 Dividing cells from stratum germinativum push up
through this layer
 Still some cell division
Stratum Granulosum
 “Grainy layer”
 3-5 cell layers thick
 Cells stop dividing, start producing proteins  grainy appearance
 keratin:
 tough, fibrous protein
 makes up hair and nails
  water resistant, not waterproof
 keratohyalin
 dense granules
 cross-link keratin fibers
  tightly interlocked cell layers
 Cells
 thinner, flatter, less permeable
 further from papillary plexus, start to die
Stratum Lucidum
 “Clear layer”
 Cells flattened, densely packed, filled with keratin  barrier
to water
 Only in thick skin (on palms and soles)
Stratum Corneum
 “Horn/hard layer” on exposed surface of skin
 15-30 cell layers of dead cells (far from nutrients in dermis);
durable, expendable  protective function
 Cells filled with keratin (= keratinized)  water-resistance (not
waterproof)
 Cells tightly interconnected by desmosomes so are sloughed off in
sheets
 Cells remain for 2 weeks (total of 6 weeks from origin in stratum
germinativum to sloughing)
2 Kinds of Skin
 Thin skin
 Has 4 layers of keratinocytes (missing stratum lucidum)
 Covers most of body
 Thick skin
 Has all 5 layers of keratinocytes
 Covers heavily abraded body surfaces, e.g., palms of hands, soles
of feet
Dermis
 Located between epidermis and subcutaneous layer
 Contains
 Blood and lymph vessels
 Nerve fibers and sensory receptors
 Tactile (Meissner’s) corpuscles – sensitive to light touch; located in
dermal papilla
 Lamellated (Pacinian) corpuscles – sensitive to deep pressure and
vibration
 Accessory organs (of epidermal origin), e.g., hair follicles,
sweat glands
Components of Dermis
 2 major components – boundaries indistinct
 Papillary layer
 Reticular layer
 Associated structures
 Papillary plexus = branching network of small arteries in
papillary layer of dermis which provide blood to capillary loops
that follow contours of epidermis-dermis boundary
Papillary Layer
 Has dermal papillae projecting between epidermal ridges
 Consists of areolar tissue
 Contains smaller capillaries, lymphatics, and sensory neurons
Reticular Layer
 Deep to papillary layer
 Consists of dense irregular connective tissue
 Contains
 Larger blood vessels, lymph vessels, and nerve fibers
 Collagen and elastic fibers 
 Strength and elasticity
 Flexibility
Dermatitis
 An inflammation of the papillary layer
 Caused by infection, radiation, mechanical irritation, or
chemicals (e.g., poison ivy)
 Characterized by itch or pain
Subcutaneous Layer
 aka hypodermis (“below dermis”), superficial fascia
 Highly vascularized – contains large arteries and veins;
site of subcu injections
 Separates integument from deep fascia around other
organs, e.g., muscles and bones
 Stabilizes position of skin relative to underlying tissues,
e.g., skeletal muscles or other organs, while permitting
independent movement
Structure of Subcutaneous Layer
 Consists of
 Elastic areolar (loose) connective tissue
 Adipose tissue (energy reserve, shock absorber)
Accessory Structures of the Integumentary
System
 Derived from epidermis
 Located in dermis
 Extend through epidermis to skin surface
 Include:
 Hair follicles and hairs
 Exocrine glands
 Nails
Structure of a Hair and Follicle
Figure 5–10a
Hair Follicles
 Living organs
 Produce “nonliving” hairs; complex process involving dermis
and epidermis
 Extend deep into/through dermis and into underlying
subcutaneous layer
 Wrapped in dense connective tissue sheath of dermis
Follicle Wall
 Composed of epithelial cells
 Cells organized into 3 concentric layers (from outside
in)
 Glassy membrane:
 Thickened basal lamina
 External root sheath:
 Widest layer
 Internal root sheath:
 Contacts cuticle (outer layer of hair)
Structure of a Hair and Follicle
Figure 5–10
Structure of a Hair Follicle
 Hair bulb
 Bulbous mass of epithelial cells
 Hair matrix
 Layer of epithelial cells in central, deepest part of follicle
 Site where cell division begins that produces hair
 Cells gradually pushed toward surface as hair gets longer
 Hair papilla
 At base of follicle (below matrix)
 “Peg” of connective tissue that contains capillaries and nerves
 If damaged, hair will not grow
Structure of a Hair and Follicle
Figure 5–10
Hair Structure
 Hair root
 Lower part of hair
 Begins at base of hair (bulb) and extends about halfway to skin
surface
 Anchors hair into skin;
 Hair shaft
 Upper part of hair
 Extends from above the root to above the skin surface
Structure of a Hair and Follicle
Figure 5–10
Layers Within Hair
 Cuticle
 Outer surface
 Layer of overlapping, dead keratinized cells
 Contains hard keratin  hair stiffness
 Cortex
 Intermediate layer below cuticle
 Also contains hard keratin
 Medulla
 Middle layer, central core
 Contains soft keratin
 Flexible
Structure of a Hair and Follicle
Figure 5–10
Associated Structures
 Arrector pili muscle
 Involuntary smooth muscle
 Contractions cause hairs to stand up  “goose bumps”
Exocrine Glands
 Sebaceous (oil) glands:
 holocrine glands
 secrete sebum
 Sweat (sudoriferous) glands:
 merocrine glands
 apocrine glands
Types of Sweat Glands
 Apocrine:
 Associated with hair follicles
 Found in armpits, around nipples, and groin
 Merocrine:
 Widely distributed on body surface
 Especially on palms and soles
Merocrine Sweat Glands
 Also called eccrine glands
 Smaller but more numerous
 Coiled, tubular glands
 Watery secretion = sensible perspiration (produced by
glands) vs. insensible perspiration which is the loss of fluid by
evaporation through the stratum corneum
Nails
 Nonliving structures; made of dead cells packed with keratin
 Form on dorsal surface of tips of fingers and toes
 Function = protect fingers and toes
 Metabolic disorders can change nail structure, e.g., shape,
appearance; can assist in diagnosis
Nail Structure
 Nail body - Superficial, visible portion
 Nail bed – area of epidermis under nail body
 Nail root – epidermal fold not visible from surface; where nail
production occurs
 Eponychium – extends over exposed nail forming cuticle
 Hyponychium – skin beneath free edge of nail
 Lunula (“moons”) pale crescent at base of nail where underlying
blood vessels may be obscured
Structure of a Nail
Figure 5–13