L4: Integument

Question 1

What is integument?

Answer 1

skin covering surface of body and specialized derivatives of skin (nails and claws, hair, sebaceous and sweat glands, teeth; non-mammals= feathers and scales)

Question 2

Integument functions

Answer 2

• protection of underlying tissues
• prevents desiccation (dehydration) -amniotes
• provides insulation (hair and feathers in birds and mammals)
• regulates heat loss by changing in hair position or increased evaporative water loss (sweating)
• reception of tactile, thermal or pain stimuli
• removal of excess water and salts
• production of vitamin D
• respiration in amphibians

Question 3

Skin is composed of 2 layers with another layer underneath. Name them (describing is in other slides)

Answer 3

Epidermis

Dermis

subcutaneous layer, fascia.

Question 4

Epidermis

Answer 4

upper layer, ectodermal origin; specialized epithelium.

In mammals, composed of stratified squamous, can be thick or thin depending on stresses on that area of skin

can also be keratinized or nonkeratinized.

Question 5

Dermis

Answer 5

below epidermis

mesodermal origin

dense irregular CT, thicker than epidermis

sensory endings (tactile, thermal, pain) found throughout

Question 6

Tela subcutanea

Answer 6

fascia, subcutaneous layer

underlies dermis

areolar to adipose CT

connects skin to structures underneath

lots of fat; holds skin in place

Question 7

General structure of the epidermis

Answer 7

Epidermis conforms to irregularities in
dermis (e.g., fingerprints) or fills in valleys
and is thin over dermal ridges (smooth skin).

• Epidermis of thick skin (palms and soles)
has 5 distinct layers.

• Epidermal cells are continuously replaced
as upper cells die and become keratinized.

Question 8

Name the layers of the epidermis

Answer 8

Stratum germinativum

Stratum spinosum

stratum granulosum

stratum lucidum

stratum corneum

Question 9

Stratum germinativum

Answer 9

single layer of low columnar cells, gives
rise to keratinocytes (epidermal cells that transform as they move up in the epidermis eventually forming keratin “scales”); underlain by basal lamina to which it is attached by hemidesmosomes;

functions as the main mitotically active or germinative layer

Question 10

Stratum spinosum

Answer 10

several cells thick, polyhedral cells with
interconnecting cytoplasmic processes (“prickle cells”) - contact between cells occurs via desmosomes at process ends so no cytoplasmic continuity; tonofilaments (keratin) present in cytoskeleton enable cells to withstand abrasion; mitotically active

Question 11

Stratum granulosum

Answer 11

3-5 cells thick, flattened polyhedral cells; nuclei
 lack nucleolus (evidence for decreased cellular activity); cytoplasm contains keratohyalin granules - involved in keratin formation and associated intimately with tonofilaments (keratohyalin + tonofilaments = soft keratin)

Question 12

Strtum lucidum

Answer 12

3-5 cells thick

pale-staining translucent layer

cells are dead and tightly packed

nuclei indistinct or absent

keratohyalin present (secreted by granules)

Question 13

stratum corneum

Answer 13

composed of clear dead scale-like cells without a nucleus

keratohyalin abundant

cytplasm replaced with keratin from tonofilaments mainly

dead cells are continually sloughed off (desquamation)

Question 14

Epidermal structure: staining of keratohyalin, changes in nuclei, function of stratum granulosum

Answer 14

Keratohyalin is very basophilic, so basophilia
increases away from basal lamina

• Nuclei become pycnotic (more compact,
densely stained) away from basal lamina

• Stratum granulosum produces vitamin D
(cholecalciferol)

– Requires UV irradiation of precursor molecule (7-
dehydrocholesterol)

– Vitamin D increases intestinal Ca2+ absorption and is
important in proper ossification/remodeling of bone

Question 15

Describe thin skin (layers, pigmentation)

Answer 15

All layers are usually present but reduced in
thickness, stratum lucidum may be absent;
keratinization is less marked; hair is present in
thin skin of mammals

• Thin skin pigmentation (or lack of it) is due to
presence of melanin (pigment) in epidermis

– Melanin synthesized by melanocytes present in upper dermis or between cells of stratum
germinativum

– Precise details of secretion not certain, but thought that vesicles containing melanin in cell processes of melanocytes become pinched off and taken into cells of stratum germinativum by phagocytosis

– Melanin is synthesized and released in response to UV irradiation - leads to suntan and acts to protect cells from harmful UV irradiation

Question 16

2 layers of the dermis

Answer 16

1. Papillary Layer = next to epidermis, contains high vascularity
2. Reticular Layer = below #1

• Epidermis (being an epithelium) is avascular so
dermis brings blood vessels into close proximity in papillary layer

• Dermis is folded into papillae which extend into
epidermis (papillary layer)

• Composed of dense irregular CT with collagen
and elastic fibers, less dense in papillary layer

Question 17

How do hair follicles start? What is the follicle surrounded by then?

Answer 17

Develop as invagination of epidermis into
dermis (same process as for other skin
derivatives)

• Invagination continues passing through
dermis and into subcutaneous tissue below

• Follicle surrounded by CT sheath from
dermis and is closely associated with
sebaceous glands and arrector pili muscles
(smooth muscle strands, act to elevate hair
and squeeze sebum into follicle)

Question 18

Define the external and internal rooth sheaths, the hair matrix, and the dermal papilla.

Answer 18

External Root Sheath = simple tubular invagination
of epidermis

** Internal Root Sheath** = lining of soft keratin, similar
to that at surface of epidermis, surrounds hair

** Hair Matrix** = proliferating mass of cells at base of
follicle

Dermal Papilla = extends into hair matrix providing
nutrients (from capillaries)

Question 19

Define the 3 layers of hair

Answer 19

central core of soft keratin (medulla)

surrounding medulla is a layer of hard keratin (stronger
form of keratin similar to that in nails, claws, etc.) = cortex

Cuticle = outermost layer of hair; composed of thin, hard
keratin; cells overlap like shingles on a roof

Question 20

Sebaceous glands (anatomy, function)

Answer 20

Sebaceous Glands = simple alveolar gland; opens
to hair follicle; secretes oily substance (sebum) that
functions as a lubricant and moisturizer for hair and
skin

• Secretion occurs by holocrine mechanism (cells die
and become part of the secretion)

• Cells in the basal layer undergo mitosis, synthesize
and accumulate lipids, become displaced toward
interior of gland and therefore are removed from
capillaries in dermis (source of nutrition) and die

• Sebaceous Gland secretion under hormonal control
(sex hormones), become more active at puberty.

– Hyperactivity leads to excessive sebum production, may become impacted and rupture into dermis, leads to inflammatory response which results in acne

Question 21

Eccrine sweat glands

Answer 21

Eccrine Sweat Glands = simple tubular glands
with coiled secretory unit, generally located
beneath dermis in subcutaneous layer

• Merocrine secretion (exocytosis)
• Abundant in thick skin (sweaty palms)

• Myoepithelial cells surround secretory portion
of gland

• Sweat composition = water, ions (Na+, K+,
Cl-), waste products (urea, ammonia, lactic
acid)

Question 22

apocrine sweat glands

Answer 22

Apocrine Sweat Glands = simple tubular
glands that open into hair follicle, secrete
by merocrine mechanism (exocytosis)

• Limited to armpits, breasts, pubic regions

• Secrete only after puberty, secretion is a
cloudy substance that becomes odiferous
upon bacterial degeneration

• Thought that these glands served as
distinctive recognition signals and sex
attractants in human ancestors

Question 23

Ceruminous glands

Answer 23

produce ear wax, these glands are considered modified sweat glands (spiral structure)

Question 24

meibomian glands

Answer 24

secretion lubricates surface of eye, cornea

• located in upper eyelid
• merocrine secretion
• compound alveolar gland

Question 25

mammary glands

Answer 25

will treat in detail with female repro system although they are modified skin glands

Question 26

Free nerve endings

Answer 26

cutaneous sensory receptors

sensory endings in deep layers of epidermis and papillary layer of dermis

responsive to pain, temp, movement (associated with hair follicles)

Question 27

merkel cell complexes

Answer 27

merkel cells are found in stratum germinativum, particularly abundant in fingertips

• nucleus is oblong and usually parallel to basal lamina
• these cells contain granules of unknown functiona round the nucleus and in cell processes
• merkel cells interact with free nerve endings to form a complex that is thought to function in mechanoreception

Question 28

pacinian corpuscle

Answer 28

distributed throughout dermis
and subcutaneous layer; responsive to pressure;
structure is like an onion bulb, the nerve ending is
surrounded by concentric layers of flat cells (modified
Schwann cells)

Question 29

Meissner’s corpuscle

Answer 29

areas of high tactile receptivity
(e.g., fingertips); responsive to touch; corpuscle is
ovoid and contains a stack of flattened cells (modified
Schwann cells) intertwined with nerve endings and
surrounded by a CT capsule; found in upper dermis

Question 30

ruffini corpuscle

Answer 30

present in deep dermis and
subcutaneous layer; spindle-shaped corpuscles; serve
as mechanoreceptors (tension)

Question 31

krause end bulbs

Answer 31

present in dermis

thick capsule with branched, coiled nerve endings; may be responsive to tension or cold