Integumentary 2 Flashcards
What are the functions of the dermis?
- Gives the strength and elasticity to skin
- Contains many of the epidermal appendages, nerve corpuscles, and glands
- Contains the smooth muscle cells that move the hairs
- Around areole, penis, scrotum and perineum,, smooth muscle cells form a loose plexus in the reticular layer
- This accounts for the puckering of the skin at these sites, particularly in erectile organs
What is the papillary layer of the dermis?
- superficial layer
- loose connective tissue(more cells)
- contains blood vessels
- predominantly type 1 and 3 collagen fibers
- the elastic fibers are threadlike & form an irregular network
- Relatively thin and includes the substance of the dermal papillae and dermal ridges
Contains Meissner’s corpuscles
Describe the reticular layer of the dermis
- considerably thicker than and deep to papillary layer
- dense irregular connective tissue (less cells )
- Characterized by thick irregular bundles of mostly type 1 collagen and courser elastic fubers
What is the physiological basis for fingerprinting?
Areas of increased mechanical stress has deeper epidermal ridges and longer, more closely spaced dermal papillae
Responsible for fingerprinting
What are the associated appendages of the dermis?
- hair follicles and hair
- sweat glands
- sebaceous glands
- nails
- mammary glands
What are epithelial appendages?
All are down growths of the epidermis inti the dermis during embryological development
Modified to perform specific duties
Epithelial appendages include…
Hair follicles and hair
-nails
- glands
- eccrine
- sebaceous
- apocrine
Describe nails as epithelial appendages
Hard plates of epidermal keratinized cells
Present on the dorsal surface on the distal phalanx of the fingers and toes
What are the functions of the nail?
Help with grip
Gives protection
What are the parts of the nail?
Nail plate:
- The visible part of the nail
- rests on the nail bed (epidermis of the skin-hyponychium) and nail matrix
Nail root
- Found proximal to the nail nail plate
- covered with a fold of skin (eponychium)
What is the nail matrix?
Nail matrix- lies deep to (beneath) the nail root
Cells from here proliferate to form the nail itself
-Grows 1 min/week by deposition of hard keratin
What are hair follicles?
- Cylindrical shafts composed of keratin
- extends into the hypodermis
- produced in follicles
- associated with sebaceous gland
- hair follicle plus sebaceous gland and smooth muscle (arrector pili)= pilosebaceous organ/unit
Where is the fair follicle located?
In thin skin only
What does the hair follicle consist of?
- Infundibulum
- Isthmus
- Inferior segment
What does the bulb of the hair follicle consist of?
Bulb contains the matrix cells for hair formation
-melanocytes stem cells are found in the bulb
Explain the process of hair follicle formation
- matrix cells contribute to formation of the internal root sheath and the hair shaft
- keratogenous zone: matrix cells undergo keratinization as soon as they pass through this zone
- They fully keratinized hair consisting of hard keratin is not followed by the internal root sheath
- It is separated from the underlying dermis via a thick basal laminal (glassy membrane)
Summarize the process of hair growth
Cyclical process
- occurs in 3 phases:
- Long phase of activate growth (anagen)
- short phase of involution (catagen)
- short inactive phase (telogen)
Growth cycle varies from site to site
- scalp hair follicles have anagen growth phase of 2 years and a short telogen of a few months - Pubuc hairs, coarse trunk hair, eyelashes, eyebrows have a short growth phase (anagen) and a relatively long resting phase (telogen) hence they are not so long
Describe sebaceous glands as epidermal appendages
-simple branched acinar gland
- secretory portion
- located deeper dermis
- Opens into hair follicle
- secretion is holocrine
- product is sebum
- poor staining with H&E
- Prevents the hair from becoming dry and brittle
Summarize Eccrine sweat glands
Found in thick & thin skin
Simple coiled tubular glands
Innervation: cholinergic
Describe the secretory portion of the eccrine sweat glands
Secretory portion is in the deep dermis,
-undergoes Merocrine mode of secretion
Contains:
-clear cells-abundant glycogen stains well with PAS
-Dark cells- abundant rER and secretory granules
-Myoepithelial cells-basal aspect of the secretory ligament
Describe the duct of the eccrine sweat gland
Duct passes through the dermis and epidermis to open onto the surface
-gentle spiral course to the epidermis which becomes tighter toward the surface
-composed of stratified cuboidal epithelium consisting of a basal layer and a luminal layer
Summarize apocrine glands as
Found only in armpit and perineum
Coiled tubular glands
Describe the secretory portion of the apocrine gland
Secretory portion: located in the dermis or even hypodermis
- Lumen larger than eccrine sweat glands
- Secretion mode- merocrine
- opens into the hair follicle
- secretes pheromones
What are the ducts of the apocrine glands?
Ducts are straight
-lined by stratified cuboidal epithelium
-have a narrow lumen
Summarize nerve supply of the skin
- free nerve endings
- Pacinian corpuscles( pressure changes & vibrations)
- Merkel’s corpuscle
- Meissner’s cirpuscles(light touch)
- Ruffini’s (stretch & torque) corpuscles
Sensory receptors of various types which are peripheral terminals of sensory nerves
Secretomotor nerve endings to the blood vessels, arrector pili muscles and sweat glands
What are free nerve endings?
Occupy papillary dermis and send twigs into the epidermis (terminate in the stratum granulosum )
- most numerous
- do not possess any myelin or connective tissue
What are the functions of the free nerve?
Subserve multiple sensory modalities
-pain, find touch, itching, temperature(heat and cold)
Networks of free dermal endings surround most hair follicles
- attach to their outer root sheath
- very sensitive to hair movement and serve as mechanoreceptors
This relationship imparts a sophisticated degree of specialization in the receptors that surround tactile hairs as is found in the whiskers of certain animals in which each represents its own area on the cortex
What is the function of the Pacinian corpuscle?
Deep pressure and vibration
What is the structure of the Pacinian Corpuscles?
- Large, ovoid structures
- Found in deep dermis and hypodermis
- Have macroscopic dimensions more than 1mm along their long axis
- composed of a myelinated nerve ending surrounded by a capsule structure
- nerve loses its myelin sheath after entering capsule
- the unmyelinated portion is covered by a series of tightly packed, flattened Schwann cell lamellae that form the inner core of the corpuscle
- The remainder is formed by a series of concentric lamellae
What is the gross anatomy of Meissner’s corpuscle?
Touch receptors particularly responsive to low frequency stimuli
- tapered cylinders
- 150 microns along their long axons
- Perpendicular to the skin surface
What is the structure function of Meissner’s corpuscle?
- Dermal papillae just beneath the epidermal basal lamina
- Appears as twisted skin of wool
- There are one or two unmyelinated nerve endings of myelinated nerve fibers follow spiral paths in the corpuscle
- The cellular component consist of flattened Schwann cells that form several irregular lamellae through which the axons course to the pole of the corpuscle
Describe Ruffini’s corpuscle
Simplest and have an elongated fusiform shape
1-2 microns
Thin connective tissue capsule surrounding a fluid filled space
Collagen fibers from surrounding connective tissue pass through the capsule
Describe the axons if the Ruffini’s corpuscle
Single myelinated fiber enters the capsule
- loose it’s myelin sheath
- branches to form a dense arborization of fine axonal endings of each terminating in a small knoblike bulb
The axonal endings are dispersed and intertwined inside the capsule
The axonal endings respond to displacement of the collagen fibers induced by sustained or continuous mechanical stress and so to respond to stretch and torque
What is Merkel’s corpuscle?
-Merkel’s cell in communication with expanded terminal bulb of afferent myelinated nerve fibers= Merkel’s corpuscle
What is the function of Merkel’s corpuscle?
Detect touch sensations
Where are Merkel’s Corpuscles most abundant?
Most abundant in skin where sensory perceptions is acute (fingertips)
What are contained in Merkel’s corpuscles ?
- cytoplasm contains neurosecretory granules
- express antigenic markers of both epidermal and neural type
