Histo(topic3)Appendages

SKIN APPENDAGES

First developed during the ______ trimester of the intrauterine development.

• Roots of the surface of simple epithelium into the developing subepithelial layers of _________.

• Forming the dermis & epidermis.

• Appendages includes:

✓ Hair

✓ Hair Follicles

✓ Sebaceous Glands

✓ Sweat Glands

✓ Eccrine Glands

✓ Apocrine Glands

✓ Nails

(just read)

FUNCTIONS:

• Reserve epidermis in the re-epithelialization after skin injury. (By migration of Keratinocytes from the adnexal epithelium of the skin.)

• Example: Wound on the scalp and face will heal rapidly in the process of re-epithellialization due to the presence of numerous Pilosebaceous Unit (Hair Follicles, Sebaceous Gland & Arrector Pili) compare to the nonhairy skin of the back.

HAIR

Can be found all over the body except for the thick skin of the _______ and _______

• Plays a vital role in body’s _______.

✓ _______ – regulates body temperature

✓ _______ – for the growth and development of hairs. ✓ _______ – stem cells for differentiation into various cell types that will make up the hair.

HAIR FOLLICLE MORPHOGENESIS

_______ in the fetal dermis collect immediately below the basal layer of the epidermis

• Epidermal buds grow down into the dermis

• Developing follicles forms at an angle to the skin surface and continues to grow downwards.

• At the base, the column of cells widens forming the bulb

The bulb is surrounded by small portion of _______

HAIR FOLLICLE

2 Buds are formed along one side of the Fetal Follicle:

✓ _______– develops into sebaceous gland

✓ _______ – becomes attachment for the arrector pili muscle

• _______was formed in the opposite side of the Fetal Follice – gives rise to the _______ Sweat Gland.

• Pilosebaceous Unit compose of:

✓ _______

✓ _______

✓ _______

3 Vertical Segments of Hair Follicle

Vertical Segments of Hair Follicle ?

- uppermost portion; above sebaceous gland

- extends to the opening of sebaceous glands

Vertical Segments of Hair Follicle?

- between the sebaceous gland and insertion part of the arrector pili muscle

- Internal Root Sheath is fully keratinizes and sheds within this segment

Vertical Segments of Hair Follicle ?

- location of hair bulb

Base, bulbous expansion and invaginated of Dermal Papllae (a tough vascularized loose connective tissue).

• Highly vascularized

• Contains melanocytes

• It has Cell Matrix (rapidly proliferating cells that produces the hair shaft, internal root sheath & external root sheath)

• Subjected to cycle of involution and regeneration throughout the life

ANATOMY OF HAIR FOLLICLE

Hair Follicle grow in an upward direction from the hair bulb; towards the skin surface

• 5 Epithelial Layers was formed.

✓ The 3 inner layers undergo keratinization to form the hair shaft or the hair, these includes the:

- __________

- __________

- __________

✓ The 2 layers form the __________ & __________

????

• Tubular Structure – formed of perifollicular connective tissue and epithelium; also invaginates the epidermis.

• The hair follicle is surrounded the Internal Root Sheath & External Rooth Shealth

• Grows up to 0.37 mm/day or approximately 1 cm/month.

what root sheath?

✓ Separates hair follicle from the dermis hyaline layer.

✓ Separated from the connected tissue sheath by a glassy membrane.

✓ Homogenous appearance

✓ Covers the internal root sheath and extends all the way the epidermis until to the basal & spinous layer.

✓ External epithelial layer merges with the epidermis of the sebaceous gland.

what root sheath?

✓ Recognized by its prominent pores

✓ Contains Eosinophilic Granules (Keratohyalin Granules) ✓ Surrounds the initial part of the hair but degenerates above the level of the sebaceous glands.

2 layers of Internal Root Sheath

Layers of Internal Root Sheath?

- thin, paler epithelial stratum

- outer single layer of cuboidal cells

- indirect contact with the outermost parts of hair follicle which present a downward growth of the epidermis

Layers of Internal Root Sheath?

- thin, granular epithelia stratum

- single of double layer of flattened cells that will form the middle plate of internal root sheath.

* These 2 layers become indistinguishable as they fused with one another and merge to the cells in the expanded part of the hair follicle, called the hair bulb.

Contains melanin pigment

• Present in germinative layer of the hair bulb

• Composed of cuticle, cortex & medulla

• When the hair shaft is matured, the thin pale stained cuticle layer surrounds the pigmented cortex and pale medulla.

HAIR SHAFT parts

HAIR SHAFT parts?

– thin, pale stained

- surrounds the cortex and medulla

HAIR SHAFT part?

– peripherally to the medulla

- contains cuboidal cells

- cells undergo differentiation into keratin filled cells

HAIR SHAFT part?

– central part of the shaft

- contains large vacuolated cells present only in thick hairs

types of hairs

type of hair?

✓ Fetal or newborn hair

✓ Characterize by fine hair

✓ Replace by vellus and terminal hairs

type of hair?

✓ Fine, light colored

✓ Narrow hair shaft

✓ Thin inner root sheath

✓ Rooted in papillary or reticular dermis

type of hair?

✓ Coarse, thick

✓ Dark (except blondes)

STAGES OF HAIR GROWTH (3)

Occurs in cyclical manner

• Follicle is an independent unit

* Humans does not shed synchronously

STAGE OF HAIR GROWTH?

- Transition Phase

- 1 to 2 weeks

STAGE OF HAIR GROWTH?

- Active Growth Phase

- 2 to 6 years

- Long period of mitotic activity and growth

STAGE OF HAIR GROWTH?

Resting Stage - Dermal papilla separated from follicle - Long period of in activity causing the hair to shed before turning anagen stage

STAGE OF HAIR GROWTH?

✓ Active growth phase

✓ Up to 0.37 mm/day growth on scalp

✓ Pigmented bulb in internal root sheath

STAGE OF HAIR GROWTH?

✓ Involution

✓ Numerous apoptic cells in the outer root sheath

Resting Phase

✓ Eyelashes have a short ____ and long _____

✓ Non-pigmented bulb with a shaggy lower boarder (_________- appearance)

HAIR SHAPE

Dimensions and curvature of the inner root sheath determine the shape of the hair.

• Scalp hairs of African and Caucasians descent is ____ causing their hair to be curly.

• Pubic hair, facial hair & eyelashes are ____ in shape.

HAIR COLOR

Depends on degree of ______

• Also in the distribution of melanosomes with the hair shaft

• ___ contains melanocytes that synthesizes melanin • Melanin is transferred to the keratinocytes of the bulb matrix the process is called ______

✓ Autoimmune

✓ Peribulbar Lymphocytic Infiltrates

✓ Causing the arrest of anagen phase

✓ Premature termination of anagen phase

✓ Increase telogen phase

✓ Most common type of hair loss

✓ Characterize by excessive and diffused loss of hairs

The skin includes 3 types of exocrine glands:

SEBACEOUS GLANDS

Associated with hair follicles (pilosebaceous unit)

• Lateral protrusions from the hair follicle

• Simple of branched alveolar in morphology appearing like a bunch of grapes (the acini of these glands are classic examples of holocrine secretion)

• ______ gland – total disintegration of secretory cells with sebum

✓ secretes an oily mixture of lipids into hair follicles known as Sebum.

✓ Sebum production is an example of holocrine secretion because the entire cell dies and contributes to the secretory products.

• Basal layer of flattened epithelial cells on the basal lamina

• Sebocytes – filled with small fat droplets

• Near the duct, the cells disintegrate releasing the main secretory product, the sebum.

• Sebaceous glands are embedded in the dermis over most of the body, except in the thick, glabrous skin of the palms and soles.

• There is an average of about 100 such glands per square centimeter of skin, but the frequency increases to 400- 900/cm2 in the face and scalp

• Sebaceous glands are branched acinar glands with several acini converging at a short duct that usually empties into the upper portion of a hair follicle

Sebum

• Mixture of lipids (wax, esters, squalene, cholesterol, and triglycerides)

• Increases at puberty

• Stimulated by androgens

• Secretion from sebaceous glands increases greatly at puberty, stimulated primarily by testosterone in men and by ovarian and adrenal androgens in women.

• Sebum helps maintain the stratum corneum and hair shafts and exerts weak antibacterial and antifungal properties.

• Found everywhere on the body except the palms and soles

✓ More abundant in the scalp, face. Midline of the back, perineum, and orifices of the body

✓ They are also found in non- hairy sites which includes the:

- Eyelids: _______

- Buccal mucosa & vermilion of lip: _____

- Areola of women: ______

- Labia minora & glans: _____

o Inflammation of the pilosebaceous unit

• Seborrheic dermatitis (dandruff)

o Found in areas rich in sebaceous glands

o form of eczema that appears on areas with high concentration of sebaceous glands like the upper back, nose, scalp.

✓ Each hair follicle has ……. fibers

✓ It consists of a bundle of smooth muscle fibers. This muscle inserts at one end into the sheath of the follicle just below the sebaceous gland and the other end into the dermal papillary area beneath the epidermis.

✓ Part of the pilosebaceous unit

✓ Oblique bands of smooth muscle inserted into the middle of hair follicle

✓ Controlled by the _______

✓ The contraction of arrector pili muscle erects the hair shaft. It depresses the skin where it inserts because of the connections it has to the dermal layer. It will produce a small bump on the surface of skin often called your goosebumps. small bump on the surface of skin often called your _______ .

• Contraction: “_______ ”

Found in palms, soles, and forehead

• ……… /eccrine in type

• Secretion discharged by exocytosis

• Simple coiled tubular in morphology

• Stimulus is heat, under control of hypothalamic thermostat (Sweating is a physiologic response to increased body temperature during physical exercise or thermal stress and is the most effective means of temperature regulation of humans)

• The secretory component is generally pale staining than the dots and consists of an unusual stratified cuboidal epithelium

• widely distributed in the skin and are most numerous on the foot soles (620/cm2 )

• Collectively the 3 million eccrine sweat glands of the average person approximately equal the mass of a kidney and produce as much as 10 L/d, a secretory rate far exceeding that of other exocrine glands.

✓ Duct opens into epidermis as sweat pre, re-absorb sodium without water

sweat ducts (2) (under eccrine gland)

SECRETORY DUCTS

• Shows only one distinct layer composed of secretory cells

• 3 distinct cell types:

what distinct cell type of secretory duct?

- At the basal lamina

- Contract to move watery substance to the duct

what distinct cell type of secretory duct?

- Produce sweat

- Transports interstitial fluid from the dermis, either directly into the gland’s lumen or into intercellular canaliculi that open to the lumen

what distinct cell type of secretory duct?

- Eosinophilic granules at the lumen

- Merocrine secretion to release a poorly understood mixture of glycoproteins with bactericidal activity.

• Double layer (2 layers of ________ cells)

• It opens into the epidermis as a sweat pore, and it is biochemically active as it modifies the composition of sweat because its cell membrane is rich in________

Thus, reabsorbing _____ ions prevent the excessive loss of electrolyte.

• Eosinophilic lumen

• Merges with the stratum ______ to form the sweat pore

Secretory cells are low cuboidal

• Have more numerous myoepithelial cells

myoepithelial cells - bring out secretory contents

• Non-functional until puberty

• Become functional at puberty when the sex hormones are produced

• The production of pheromones by _______

• glands is well established in many mammals.

• It is innervated by _______ nerve endings, whereas eccrine sweat glands receive _______ fibers.

apocrine gland

_______ secretion

✓ initially odorless – unpleasant odor (after bacterial decomposition)

- secretion itself is not odorous, it’s the bacterial decomposition that conjures/confers the bad smell

✓ stimuli: emotional stress, sympathetic discharge (innervated by adrenergic nerve endings vs. cholinergic fiber in eccrine)

✓ Excessive sweating (eccrine glands)

✓ Offensive odor from apocrine gland secretions and bacterial flora

Both glands (eccrine and apocrine) are coiled and tubular (under the microscope) but _______ glands are less coiled, have wider lumen, and have more myoepithelial cells.

Dorsal surfaces of terminal phalanges

NAIL STRUCTURE

Nail Apparatus

✓ Nail plate

✓ Specialized epithelia:

- Proximal nail fold

- Nail matrix

- Nail bed

- Hyponychium

✓ Proximal part of the nails

✓ Covered by a fold of skin (PROXIMAL NAIL FOLD) → ___ / ____

✓ From which the epidermal stratum corneum extend as cuticle or the eponychium.

✓ Forms the nail matrix

✓ Also knowns as the Germinal Matrix

✓ It is the area where fingernails and toenails start to grow ✓ A distal movement by proliferation and differentiation of epithelium

✓ A semilunar area of proliferative ventral surface of the nail groove

✓ 3 mm/month (fingernails) and 1 mm/month (toe nails) - In which cells divide more distally and become keratinized in the process similar to hair formation but without keratohyaline granules

✓ Complete replacement of a finger nail will require 6 months while for toe nail its 12 to 18 months.

Nail Matrix

• ____

✓ Crescent-shaped white area

✓ Opaque nail matrix and immature nail plate below it

✓ Nail root matures and hardens to form nail plate.

Nail Plate

✓ Dense keratinized appendage

✓ Hard keratin

✓ Continuous growth in matrix pushes the nail plate forward over the nail bed.

✓ It is the visible part of the nail from the lunula to the free edge

Nail Bed

✓ Contains only basal and spinous epidermal layers (the last 2 of the epidermal layers)

✓ Nail Root matures and hardens to form the Nail Plate

• It is the skin underneath the nails

• Distal end of the plate (become free of nail bed at the epidermal fold), it is the skin just under the free edge of the nail

✓ Abnormal keratinization of the nail matrix

BLOOD SUPPLY

• Cutaneous plexus: between the dermis and subcutis

✓ Larger blood vessels

• Subpapillary or superficial plexus: between the papillary and reticular dermis

✓ Capillaries, end arterioles, venules

• ________: special type of AV anastomosis for temperature regulation; fingers, toes, and nails.

Small arteries (deep vascular plexus) and arterioles (dermis) possess 3 layers:

✓ ______ composed of endothelial cells and an internal elastic lamina

✓ _______ – contains collagen, elastic fibers, and several concentric layers of smooth muscle cells bounded by an external elastic lamina (in arteries)

✓ _______ – composed of fibrocytes, collagen, and elastic fibers

• Walls of veins generally are thinner compared to arteries and less clearly divided into three classic layers

Nerve Endings

✓ Both efferent and afferent nerve supplies.

✓ Free nerve endings.

- Can be myelinated or unmyelinated

- Pain, itch, temperature

✓ Specialized encapsulated nerve endings.

✓ _________: Mechanoreceptor

✓ Prominent in papillary dermis of fingers, toes, soles, and palms.

✓ _________: deep pressure and vibration (deep in the palms & soles)

Thick skin (yes/no/increase/decrease)

✓ Palms of hands, fingers, soles, feet

✓ Thickness of epidermis ___

✓____ sweat glands

✓ ___ pilosebaceous follicles

✓ Grooves and ridges ___ because of tall dermal papillae

✓ ___arterio-venous anastomosis

• Thin skin (yes/no/increase/decrease)

✓ Other regions _____ palms, soles, fingers, toes

✓ ___ epidermis

✓ _____number of sweat glands

✓ _____ of pilosebaceous follicles

✓ ______ ridges and grooves with checkered networks of lines

✓ _____ or _____ arteriole-venous anastomosis