Lecture 3: Integument And Barriers To Infection Flashcards
Where is thick skin found?
Palms and soles
Thick skin is composed of ______ layers, lacks _______, and may be characterized by fingerprints
5
Hair
Where is thin skin found?
Everywhere on the body except the palms and soles
Thin skin is made up of _____ layers, contains _____ and _______ glands, and contains hair follicles
4
Sweat
Sebaceous
Thin skin is made up of 4 layers, while thick skin is made up of 5. Which layer is missing from thin skin?
Stratum lucidum
The surfaces of palms and soles have _________ ________ with intervening furrows.
Each ridge follows the outline of an underlying ___________ _________
There is a tight interface at the _________ ___________ junction via hemidesmosomes
Epidermal ridges
Dermal ridge/papilla
Dermal-epidermal
What are the 5 layers of the epidermis that are found in thick skin?
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale
The epidermis is composed of what 4 additional cell types?
Which one has immune function?
Keratinocytes
Melanocytes
Merkel cells
Langerhans cells (immune function)
The stratum basale layer of skin is mitotically __________.
Skin is replaced every ____-____ days.
It is a single layer of _____________ or low __________ cells bound to more apical ____________ via desmosomes
Active
15-30
Cuboidal; columnar; keratinocytes
Psoriasis is a skin condition resulting from the overproliferation in which skin layer?
Stratum basale
The stratum spinosum layer contains polyhedral ______________ that produce ___________, which aggregates to form ______________.
This layer thickens with pressure to produce corns and calluses.
The stratum spinosum + the stratum basale = __________ layer.
Keratinocytes; cytokeratin; tonofilaments
Malpighian
In the stratum granulosum, cells become progressively more flattened and contain ___________. It is 3-5 layers thick, cells have a distinct __________ and it is where terminal differentiation begins.
Granules
Nucleus
What type of granules, present in stratum granulosum, are basophilic and non-membrane bound?
Keratohyalin granules
What type of granules, found in stratum granulosum, are lipid-rich and function as a barrier to foreign material and water loss?
Lamellar granules
What layer of the epidermis consists of a translucent band of cells that do not contain organelles or nuclei?
Stratum lucidum
The stratum lucidum is a translucent band of cells without organelles or nuclei, but it does contain densely packed _______ filaments
Keratin
True or false: the stratum lucidum is mitotically active
False
Why does it make sense that the stratum lucidum does not contain nucleated cells?
The nucleus is lost after the granulosum layer because lucidum is no longer mitotically active. The nucleus would take up valuable space that is needed in order to pack more keratin into the cells
Stratum ________ consists of multiple layers of cells filled with mature keratin.
__________ are fully keratinized cells that are continuously shed.
In thick skin, this layer is made up of ____-____ layers.
In thin skin, this layer is made up of _____-_____ layers.
Corneum
Squames
15-40
10-20
The stratum corneum is typically the second thickest layer of the epidermis, while ___________ is the first
Stratum spinosum
Melanocytes originate in the _____ ______ and are visible from the 8th embryonic week.
They are the ____ cells to arrive in the epidermis.
The cell body is located in the stratum _______. Cytoplasmic extensions of one melanocyte establish contact with about 36 ____________, forming an epidermal-melanin unit.
Neural crest
First
Basale; keratinocytes
True or false: melanocytes and keratinocytes are associated to each other via desmosomes
False
___________ cells derive from a bone marrow cell precursor and are present in the embryonic skin 4-5 weeks after the arrival of the melanocytes
Langerhans
Langerhans cells are found in the stratum of _______ (spinosum and basale).
A langerhans cell is a peripheral __________ cell of the immune system that migrates to a local LN to present Ags to _____ cells to initiate responses to foreign antigens
Malpighi
Dendritic; T
Merkel cells derive from the ______ _______.
They appear in _________ and _________ epidermis at about 8-12 weeks gestation.
They are tactile mechanoreceptors but may also have a ___________ function.
Neural crest
Palmar; plantar
Neuroendocrine
Merkel cells are associated with the ______ _______.
Their cytoplasm contains ________.
A small _____ _____ is connected to a myelinated axon. Myelin is lacking on the short axon segment penetrating the basal lamina of the epidermis.
Basal lamina
Granules
Nerve plate
Keratinocytes are responsible for making keratin and __________ granules.
They form the ________ in stratum corneum.
They also house the pigment protein __________.
Lamellar
Squames
Melanin
What protects nuclei from UV radiation?
Melanin (pigment protein)
Once melanocytes produce melanin, where is it transfered?
Keratinocytes
What disease may result from overproliferation of melanocytes?
Melanoma
Melanin production increases in sun-exposed areas because the enzyme _____________is UV sensitive.
It is responsible for converting ___________ to ___________, which is then polymerized into melanin
Tyrosinase
Tyrosine –> DOPA (dihydroxyphenylalanine)
Langerhans cells are APCs that provide defense against pathogens. They develop in the bone marrow from a ________ precursor.
They are typically identified in the stratum _________ by their _____ cytoplasm with ______ processes.
Monocyte
Spinosum; pale; long
True or false: Merkel cells are more numerous in thin skin
False; more numerous in thick skin
The dermis is composed of CT of ____________ origin.
It contains _________ and _________ layers, as well as skin appendages, vasculature, and sensory nerve endings.
Mesodermal
Papillary; reticular
Describe the papillary layer of the dermis
Superficial layer of loose CT
Contains Meissner corpuscles (sensation) and dermal papilla
Describe the reticular layer of the dermis
Deep layer of dense irregular CT (type I collagen) with elastic fibers
More fibers and fewer cells
Are hair follicles epidermally derived or dermally derived structures?
Epidermally derived, but the follicles do extend down into the dermis
Between the papillary and reticular layers of the dermis lies the __________ ___________, consisting of capillary branches that provide a source of nutrients.
Within the reticular layer is the ___________ _________ with larger vasculature and lymphatics.
Subpapillary plexus
Cutaneous plexus
The hypodermis is loose, subcutaneous tissue containing adipocytes. What is the primary function?
Binds skin to underlying organs
Why might a surgeon recommend that their patient lose weight prior to undergoing surgery?
Fatty tissue present in the hypodermis has an extensive vascular supply, and could increase the risk of bleeding during a procedure
What is the simplest sensory receptor?
Free nerve endings
Free nerve endings are made up of numerous _________ fibers positioned along the __________-________ junction.
They relay modalities such as temperature, touch, itching, and ______
Afferent
Dermal-epidermal
Pain
_________ ________ are elliptical-shaped, encapsulated touch receptors that detect light touch or low-frequency stimuli.
Meissner Corpuscles
Meissner Corpuscles are located in dermal ________, partially surrounded by _________.
They are numerous in ___________, palms, and soles.
Papillae; epidermis
Fingertips
________ _________ are large oval structures that detect coarse touch, vibration, or pressure.
They are found deep in the __________ dermis or hypodermis.
An outer CT capsule surrounds 15-50 thin concentric layers, and movement/pressure leads to a nerve impulse
Pacinian corpuscles
Reticular
What is the primary example of merocrine glands?
Sweat glands
[note that merocrine = eccrine; and apocrine glands can also be sweat glands]
How do merocrine glands release their contents?
Via exocytosis at apical ends
What is the primary example of holocrine glands?
Sebaceous glands
How do holocrine glands release their contents?
Disintegration of the cell with contents becoming the secreted product
What type of glands are mammary glands?
Apocrine
How do apocrine glands secrete their product?
Via membrane-enclosed vesicles at the apical end
The acinus of sweat (sudoriferous) glands is characterized by ____________ _______ epithelium.
____________ cells surround the acinus and expel the secretions
Simple cuboidal
Myoepithelial
The duct of sweat (sudoriferous) glands is characterized by _________ _________ epithelium (as opposed to acinus simple cuboidal).
The ducts are typically _______ staining.
Stratified cuboidal
Darker
Sebaceous glands are abundant on the face and scalp, and are often associated with the hair follicle.
They produce a lipid mixure called ________, via ___________ secretion.
They typically have a single duct made up of _________ ________ __________ epithelium.
Sebum; holocrine
Simple branched acinar
What is the purpose of the sebum produced by sebacous glands?
It is a waxy mix of triglycerides and cholesterol responsible for lubricating, softening, and waterproofing the skin
What is the difference between eccrine and apocrine sweat glands in terms of their distribution?
Eccrine sweat glands are found extensively throughout the skin
Apocrine glands are restricted to the dermis of the axilla, circumanal region, and areola
What type of sweat glands produces sweat for thermoregulation?
Eccrine
What type of sweat gland is under adrenergic regulation and responds to hormones?
Apocrine glands
Describe the sweat components of eccrine glands
Water, salt, ammonia, uric acid, and mucinogen granules
Describe apocrine secretions
Milky sweat secretion
Odorless until it mixes with bacteria
Hair follicles are epidermal derivatives. What two structures are they typically directly associated with?
Sebaceous glands
Arrector pili muscles
What are the 3 general components of hair
Hair bulb
Dermal/hair papilla
Hair matrix
What are the 3 components of the hair shaft itself?
Medulla = core of hair shaft Cortex = middle layer Cuticle = outer layer
What is the difference between vellus and terminal hair?
Vellus hair is thin and found diffusely around the body. Terminal hair is thicker and is typically generated in certain areas in response to androgenic hormones during puberty (males have more)
Nails are made up of highly keratinized cells on a bed of epidermis.
The nail _________ is the most proximal region of the nail plate, which forms from proliferating ______________.
The nail plate remains attached to the nail bed and is pushed forward by continuous growth.
The _________ is the crescent shaped white area near the nail matrix.
Root; keratinocytes
Lunula
