Lecture 3: Integument Flashcards
List functions of the skin (6)
1) Barrier
2) Homeostasis
3) Immunologic
4) Sensory
5) Endocrine
6) Excretion
What type of epithelium makes up the integumentary system?
- Keratinized stratified squamous epithelium (epidermis)
What makes up the dermis layer of the integumentary system?
Connective tissue in 2 layers:
1) loose CT = papillary
2) dense irregular = reticular
What is the purpose of a skin barrier?
- It is between the body and the environment
- Acts as a barrier against external environments entering and internal environments escaping
What is the function of homeostasis?
Helps regulate body temperature and water loss
What is the function of immunologic?
Interacts with antigens and processes them for presentation to the immune system
What does the sensory function of the skin do?
Receive information from the environment
What does the endocrine function of the skin do?
Secretes hormones, growth factors, and converts precursors of vitamin D
What does the excretion function of the skin do?
Excretion is through sweat glands of water and ions
What type of epithelium does the epidermis have?
stratified squamous, keratinized epithelium
The epidermis has 5 identifiable layers in _____ skin.
thick
How many identifiable layers does the dermis have?
2
What type of tissue makes up the dermis layer?
connective
The ______ is NOT typically considered a layer of skin.
hypodermis
What type of epithelium is ectodermal?
stratified squamous, keratinized epithelium
What are the 5 layers (strata) of the epidermis?
From Deep to Superficial
1) Stratum germinativum
2) Stratum spinosum
3) Stratum granulosum
4) Stratum lucidum
5) Stratum corneum
Which layers of the epidermis have a layer of cell mitosis?
1) Stratum germinativum
2) Stratum spinosum
What is the stratum germinativum also called?
stratum basale
What type of epithelial cells composes the stratum germinativum?
single layer of cuboidal or columnar cells which rest on a basal lamina
What attaches the basal cells to the basal lamina in stratum germinativum?
hemidesmosomes
What attaches adjacent cells in stratum germinativum?
desmosomes
What makes up the stratum spinosum? What do they form?
polygonal cells that have spiny projections that form intercellular bridges
Which layers of the epidermis are referred to as the Malpighian layer?
Stratum germinativum & Stratum spinosum
What are the non-membrane bound granules of the stratum granulosum?
basophilic and keratohyaline
What are the membrane-bound granules of the stratum granulosum?
membrane-coating granules
What do the membrane-coating granules of the stratum granulosum contain?
glycosaminoglycans and phospholipids that are extruded into extracellular space = form a barrier to microorganisms, foreign substances, and water
What do keratinocytes produce as they mature and differentiate?
keratin hyaline granules and lamellar bodies
What is the function of lamellar bodies?
involved in formation of water barrier
What is the function of keratin hyaline granules?
increase in number and release contents into the cytoplasm as the cell dies
Which layer of the epidermis is most prominent in thick skin?
stratum lucidum
What makes up the stratum lucidum?
translucent layer of acidophilic cells that are devoid of nuclei and organelles
What makes up the stratum corneum?
flattened keratin-filled cells devoid of any organelles including the nucleus
Which layer of the epidermis is called horny cells or squams?
stratum corneum
Explain levels of damage in 1st degree burns
Low yield
- Damage to superficial epidermis
- Cells of stratum germinativum remain viable and regenerate epidermis
Explain levels of damage in 2nd degree burns
Low yield
- Epidermis completely destroyed
- Remnants of sweat glands and hair follicles in the dermis are able to regenerate the epidermis
Explain levels of damage in 3rd-degree burns
Low yield
- Full-thickness burn
- Destroys epidermis and dermis
- Skin grafts are typically necessary
- Loss of body fluids can cause hypovolemia and shock (15 % of body area in adults, 10% of body area in children)
List the cells found in the epidermis (4)
1) Keratinocytes = ectodermal origin
2) Melanocytes = neural crest origin
3) Langerhans cells = dendritic, antigen-presenting cells
4) Merkel cells = specialized keratinocytes involved in touch
What is the predominant cell type in the epidermis?
keratinocytes
Keratinocytes give rise to which layer of the epidermis?
stratum corneum (protective dead cell layer)
Where does basal cell carcinoma only arise?
regions of skin containing sebaceous glands
What part of the body is basal cell carcinoma usually found?
eyelids and bridge of nose
Who does basal cell carcinoma typically affect?
Occur after age of 40 in fair-skinned individuals
What does basal cell carcinoma look like histologically?
form discrete nests or islands of cells that resemble normal basal cells
What does squamous cell carcinoma look like histologically?
- complete replacement of normal epithelium with pleomorphic epithelium
- penetrates dermis in later stages
Which layer of the epidermis are Langerhans cells mostly found?
stratum spinosum
Which type of cells are NOT attached to adjacent keratinocytes by desmosomes?
Langerhans cells
What is the role of Langerhans cells?
responsible for engulfing invading microorganisms in the epidermis and presenting antigens to lymphoid cells
What are Langerhans cells derived from? **HIGH YIELD **
Mesoderm
What technique is used to visualize Langerhans cells?
- Gold impregnation technique
- Cannot be distinguished easily in H&E-stained tissue
What are melanocytes derived from?
HIGH YIELD
neural crest cells
Which layer of the epidermis are melanocytes found?
stratum germinativum with hemidesmosomes
Which cells are NOT connected to surrounding keratinocytes by desmosomes, but can be attached to the basal lamina by hemidesmosome?
melanocytes
Melanocytes contain a large amount of which enzyme?
tyrosinase
What is the function of tyrosinase?
responsible for conversion of tyrosine through a series of steps to produce melanin
What is the process called when melanin granules are injected into keratinocytes?
cytocrine secretion
What is the role of melanin granules?
- Protect the dividing cells from UV radiation (think of forming an umbrella over the nucleus)
- Eventually, fuse with lysosomes in the keratinocytes and are degraded by the time the keratinocytes reach the stratum granulosum
Which type of cancer is 2% of skin cancers?
malignant melanoma
Why is malignant melanoma very metastatic?
B/c of their neural crest origin = highly migratory cells
Where are Merkel cells found?
thick skin where touch is acute
Why do Merkel cells appear to be mechanoreceptive cells?
associated with nerve endings
What does the papillary layer of dermis contain?
Loose CT containing:
- fibroblasts
- mast cells
-macrophages
- leukocytes = major part of the dermal papillae or pegs
What is the reticular layer of the dermis composed of?
Dense irregular CT = composed of collagen Type 1 fiber & fewer cells than papillary layer
Where is thick (glabrous) skin found?
areas exposed to greater wear and abrasion = palms of hands and soles of feet
True or False: Thick (glabrous) skin is hairless with no sebaceous glands.
True
True or False: Thin skin has all 5 epidermal layers with a prominent stratum lucidum and a thick stratum corneum.
False, thick skin
Where is thin skin found?
rest of the body
True or False: Thick skin has no distinct stratum lucidum and a quite thin stratum corneum
False, thin skin
Where is the hypodermis located?
deep to the dermis BUT NOT CONSIDERED PART OF SKIN
What is the hypodermis also called?
superficial fascia or subcutaneous CT
List appendages of the skin (5)
- hair follicles
- sweat glands
- sebaceous glands
- mammary glands
- nails
What are hair follicles?
invaginations of epidermis which during periods of growth have bulbous terminal dilations = the hair bulb
Where is the hair bulb located?
Rests upon dermal papilla = contains capillaries that nourish the hair follicle
What are the 2 types of sweat glands?
1) eccrine sweat glands
2) apocrine sweat glands
What type of glands are eccrine sweat glands? What do they secrete?
- simple, coiled tubular glands
- secrete a non-viscous fluid = evaporation of the fluid cools skin
Eccrine sweat glands are also _______.
excretory
What do eccrine sweat glands contain?
catabolites
What are myoepithelial cells?
- specialized cells that squeeze the secretions from the sweat acini
- epithelial cells NOT smooth muscle cells
Why are myoepithelial cells acidophilic?
They contain actin filaments
Where are apocrine sweat glands located?
specialized glands located in axillary, areolar, and anal regions
Where are sebaceous glands found?
- the skin of the lips
- glands of the penis
- clitoris
What do sebaceous glands secrete?
sebum by holocrine secretion
Most carcinomas of the breast are _______ (glandular)
adenocarcinomas
What occurs in stage 1 breast cancer?
<2 cm = no nodal involvement
What occurs in stage II breast cancer?
2-5cm = without nodal involvement
What occurs in stage III breast cancer?
> 5cm = with or without nodal involvement
What occurs in stage IV breast cancer?
any tumor involving the thoracic wall or skin or any tumor involving homolateral infraclavicular or supraclavicular nodes
The nail root is the _____ region of the nails
germinal
The nail bed consists of which epidermis layers?
stratum germinativum and stratum spinosum only (the malpighian layer)
What does the epithelium of the nail bed arise from?
nail matrix
The nail grows from _____ end and slides over the _____ bed.
proximal, nail
What are free nerve endings?
unmyelinated axons that penetrate the basal lamina of the epidermis to enter the stratum germinativum and spinosum
What is the ONLY type of receptor found in the cornea?
free nerve endings
What is the function of free nerve endings?
- involved in temperature and pain perception
- also function in crude touch
Where are Meissner’s corpuscles most abundant?
- thick (glabrous) skin
- the skin of the lips
- nipples
Where are Meissner’s corpuscles found?
within the dermal papillae of thick skin
What is the function of Meissner’s corpuscle?
- involved in discriminative touch
- ability to discriminate two points
Where are Pacinian corpuscles found?
dermis and hypodermis of both thick and thin skin
Where are Pacinian corpuscles most abundant?
skin of fingertips
Which layer of the epidermis are the arrows pointing to?
Stratum Corneum
Is this picture showing thick skin or thin skin?
Thick skin
Which layer of the dermis is #1?
Reticular layer
What is #1?
Dermis papillary layer
What is #2?
Epidermis
What is #3?
Arrectores pilorum
What is #4?
Dermis reticular layer
What is #1?
Apocrine sweat glands
What layer of the dermis is #1?
Papillary
What layer of the dermis is #2?
Reticular
Which type of cancer is this image showing?
Basal cell carcinoma
Which layer of the epidermis is #1?
Stratum germinativum
Which layer of the epidermis is #2?
Stratum spinosum
Which layer of the epidermis is #3?
Stratum granulosum
Which layer of the epidermis is layer #4?
Stratum lucidum
Which layer of the epidermis is layer #5?
Stratum corneum
Which layer of the epidermis are the arrows pointing to?
Stratum lucidum
Which layer of the skin is #1?
Epidermis
Which layer of the skin is #2?
Dermis
Which layer of the skin is #3? Hint: It is NOT typically considered a layer of the skin
Hypodermis
Which type of sweat glands are the arrows pointing to?
Eccrine sweat glands
Which layer of the dermis is #1?
Papillary
The stratum germinativum and stratum spinosum are referred to as this layer. What layer is the blue bracket pointing to?
Malphigan layer
What is #1?
Pacinian Corpuscle
What is #1?
Sebaceous gland
What is #2?
Papilla hair root
What is #3?
Hair follicle
What is #4?
Skeletal (striated) muscle
What are the two structures in this image
Hair follicles
Which layer of the epidermis is the blue bracket pointing to?
Stratum granulosum
What are Langerhans cells derived from? HIGH YIELD
Mesoderm
- What cell type is derived from mesoderm & functions as APCs in the stratum spinosum?
a. Melanocytes
b. Merkel cells
c. Langerhans
d. Keratinocytes
c. Langerhans
- Which of the following is typically found in thick skin?
a. Sebaceous glands
b. Meissner’s corpuscles
c. Arrector pili muscles
d. Dermal papilla
b. Meissner’s corpuscles
- Which of the following is typically found in thin skin?
a. Stratum lucidum
b. Lack of hair follicles
c. Goblet cells
d. Arrector pili muscles
d. Arrector pili muscles
- Identify the following structure:
a. Arrector pili muscle
b. Eccrine sweat gland
c. Sebaceous gland
d. Hair root
c. Sebaceous gland
- Identify the following structure:
a. Dermal papilla
b. External root sheath
c. Internal root sheath
d. Hair cuticle
a. Dermal papilla
