23 - Integument Flashcards
(67 cards)
1
Q
Where do humans have extra skin folds? Why?
A
We have extra skin folds over certain joints to prevent skin from breaking upon flexion
- Elbow
- Knuckles
- Knee joint
- Achilles tendon
2
Q
What does the integument include?
A
Integument
- Skin
- Its appendages
- Sweat glands
- Sebaceous glands
- Hair
- Nails
3
Q
What are the functions of the skin?
A
Functions:
- Protection
- Regulation of body temperature
- Reception
- Absorption
- Excretion
4
Q
How does the skin protect?
A
Protection
- The skin covers almost the entire body
- The only exception is the nails
- The skin protects from invasion from microorganisms and dehydration
5
Q
How does the skin regulate body temperature?
A
Regulation
- Sweat glands relsease sweat
- This cools down the body when the sweat is evaporated
6
Q
How does the skin function in reception?
A
Reception
- Neuroreceptors may relay pain, touch, pressure and/or position to the central nervous system (CNS)
- Thermoreceptors on our skin sense temperature
- The skin allows us to form an image of the environment around us
7
Q
How does the skin fucntion in absorption?
A
Absorption
- Absorbs ultraviolet radiation for vitamin D production
8
Q
How does the skin function in excretion?
A
Excretion
- Eliminates waste products through sweat
9
Q
What is the largest organ of the body?
A
The skin!
10
Q
How do we classify skin?
A
There are two classifications:
- Thin skin
- Thick skin
11
Q
Thin skin
A
- Covers most of the body’s surfaces
- Contains hair follicles, sebaceous glands, sweat glands, erector pilae muscles
12
Q
Thick skin
A
Thick skin…
- Covers the palms and soles of the feet
- No hair follicles are found on these surfaces
- No sebaceous glands
- Sebaceous glands are oil-producing glands that are found in hair follicles
- No erector pilae muscles
- Erector pilae muscles are smooth muscles that anchor the root of the hair follicle
- This erects hair when contracted in order to keep the body warmer
- Sweat glands ARE present
13
Q
What are the layers of the skin?
A
Two layers:
- Epidermis
- Dermis
14
Q
Epidermis
A
Epidermis
- Contains stratified squamous keratinaized epithelium
- Divided into sub-layers called “strata”
15
Q
Dermis
A
Dermis…
- Composed of two layers of connective tissue that is found under the epidermis
- Loose connective tissue that is more superficial
- Dense irregular collagenous connective tissue that is deeper
16
Q
What types of cells ar found in the epidermis?
A
Keratinocytes
- Cells that accumulate keratin
- This is the most common cell type found in the epidermis
Non-keratinocytes are also found in the epidermis
17
Q
Ridges and papilla
A
Ridges (epidermis) and papilla (dermis)
- The epidermis has folds that extend down into the dermis, known as epidermal ridges
- The dermis sends projections into the epidermis known as dermal papilla
- The two structure interdigitate
- Function
- Increase the surface area of the dermis and epidermis
- Ensure the two layers stay together and don’t slip apart
18
Q
Basal cells
A
Basal cells
- Basal cells are a layer of epidermal cells that are found where the epidermis meets the dermis
- Also called stratum basale
- This is an area of intense mitotic activity
19
Q
Basal cell migration
A
Migration
- Cell from the stratum basale (basal cells) migrate to the surface of the skin
- As they migrate, they acquire more keratin, become keratinized, then die and “slough off”
- It takes 20-30 days for the cells to migrate from the strata basale to the superficial layer of the skin
- This migration takes place mostly at night, so a good night sleep DOES make your skin look better (think beauty rest)
20
Q
Non-keratinocytes
A
Non-keratinocytes are also found in the epidermis, but not as commonly as keratinocytes are
- There are three types of non-kerantinocyes
- Langerhans cells - defense cells, protect against invading antigens
- Merkel cells - mechanoreceptors
- Melanocytes - act as umbrellas to provide UV protection
21
Q
Langerhan cells
A
Langerhan cells (dendritic cells, antigen-presenting cells)
- Langerhan cells are derived from precurors in bone marrow
- These precurosr cells enter the blood stream and travel to the epidermis
- Once in the epidermis, they differentiate into Langerhan cells, which are
22
Q
Cytoplasmic processes of Langerhans cells
A
Cytoplasmic processes
- Extensions of the Langerhan cells into the extracellular space of neighboring cells are known as cytoplasmic processes
23
Q
Function of Langerhans cells
A
Function
- Foreign bodies which invade the skin are phagocytosed by the Langerhans cells
- The LCs move a piece of what they ate (an antigen) to their cell surface
- Then they travel to a nearby lymph node, and present that antigen to immune cells (lymphocytes)
24
Q
Membrane-bound birbeck granules of Langerhans cells
A
Birbeck granules
- Have a unique, tennis racket structure
- Composed of a rod which is attached to a vesicle
- The function of birbeck granules is not well understood, but it is thought that they are a part of the defense mechanism for the skin (protection from antigens)
25
Merkel cells
Merkel cells are found in the **base of hair follicles** and **fingertips**
* Merkel cells are mechanoreceptors (tactile receptors)
* Responsible for fine/discriminating touch
* Allow our fingertips to feel detailed textures
* Merkel cells attach to keratinocytes by **desmosomes**
* **Neurite complexes** form from merkel cells, which contain unmyelinated nerve terminals
* Merkel cells are found in the **stratum basale**
26
Melanocytes
Melanocytes arise from the **neural crest**
* Melanocytes synthesize the pigment, **melanin**
* Melanocytes are located in the **stratum basale** and the **superficial dermis**
* Note that the spots and stripes on animals (leopard/zebra) are not only on the fur, but on the skin as well and are produced by concentrations of melanocytes
27
How do melanocytes convert tyrosine into melanin?
Melanocytes synthesize **tyrosinase**
* Tyrosinase is an enzyme that turns tyrosine into malanin
* Tyrosinase is synthesized at the rER then processed/packaged in the Golgi
* The Golgi relseases tyrosinase in membrane vesicles called **melanosomes**
* Melanosomes take up tyrosine from the cytoplasm
* Tyrosinase inside the melanosomes turns the tyrosine into melanin
* The melanosome because dark (now known as a melanin granules)
* The melanin granules make their way into the cytoplasmic processes of melanocytes
28
Release of melanin granules
Melanin granules can be found in the cell processes of melanocytes
* Melanocytes lie in the stratum basale (bottom layer of the epidermis)
* The cytoplasmic processes extend up into the stratum spinosum (some even enter nearby cells)
* Melanocytes release their melanin granules into nearby cells via vesicles
* **The granules will surround the nucleus of neighboring cells - this covers and protects the DNA from UV radiation**
29
Number of melanocytes
This number varies in different areas of the skin
* Dependent on the amound of sunlight the skin is exposed to
* For example, there are fewer melanocytes in the axillary fossa than on the front of the arm
* The TOTAL number of melanocytes in the body is about the same in all races
* The pigmentation of skin is not due to the number of melanocytes present
30
Pigmentation of the skin (differences between races)
Pigmentation is dependent upon...
* Tyrosinase activity
* Darker skin has increased activity
* Number of melanin granules
* Size of melanin granules
* Darker skin has larger
* Distribution of melanin granules
* Lighter skin are located more in the nucleus
* Darker skin is more scattered around the cell
* Rate of breakdown
* Dark skin break down slower
31
Vitiligo
Vitiligo is an autoimmune disease
* The body self-destructs melanocytes
* The patchy skin pigmentation is due to a decrease or a complete loss of melanocytes in certain areas
* All races and all ages can be affected
32
Albinism
In albinos...
* Melanocytes are present
* However, melanocytes do not synthesize melanin due to a _defect or absence of tyrosinase_
33
Malignant melanoma
Remember the ABCDEs...
* A = Appearance (general appearance, is it itchy?)
* B = Border (irregular, contour, notches, dimples)
* C = Color (irregular, red/black/brown, pigmentation)
* D = Diameter (larger than a pencil eraser needs removal)
* E = Evolution (any recent changes)
Risk factors include heriditary, light skin, excessive sun exposure
34
Strata of the epidermis
Strata = layers
* The epidermis is the epithelial (most superficial) layer of the skin
* The epidermis is **avascular**
* No blood vessesls
* The epidermis get nutrients from the capillaries from the underlying layer (the dermis)
35
5 strata of thick skin
Strata of thick skin, from the bottom (innermost) layer out
* **Stratum basale**
* Bottommost layer, a lot of mitosis going on here
* As the cells migrate upward, they aquire different morphological characteristics and accumulate more keratin
* **Stratum spinosum**
* Thickest layer
* **Stratum granulosum**
* **Stratum lucidum**
* Actually a sub-layer of the stratum corneum
* **Stratum coreum**
* Most superficial layer
36
Stratum Basale (Germinativum)
Stratum basale
* Single layer of columnar cells
* Basement membrane is found underneath them between the basal cells and the dermis
* Anchors the dermis to the epidermis
37
How are individual cells attached to _each other_ and to the _basement membrane_ within the stratum basale?
Attachments
* Attached to _each other_, and more superficial epidermal cells, via **desmosomes**
* Attached at the basal aspect to the _basement membrane_ via **hemidesmosomes**
38
What are the functions of the stratum basale?
Functions
* Cell renewal (regermination of the epidermis)
* Anchoring the epidermis to the underlying dermis
39
Basal cell carcinoma
Caused by chronic sun exposure
* Develops on the top of the head and in places where the skin is exposed to sunlight all the time
Pearly papule
* Arises from cells found in the stratum basale
* Slow growing and rarely metastasis
* Can be excised without issue
Subepidermal blood vessels
* These lesions contain their own blood vessels
40
Stratum spinosum function
Function
* Has numerous cell adhesions to give the skin its strength
* Allows the skin to resist abrasions
* This provides protection from outside microorganisms
41
Stratum spinosum appearance
Appearance
* Called “spinosum” because the cells appear to have spines sticking out from their cytoplasm
* Look like “railroad tracks”
* They are actually intercellular bridges between neighboring cells
42
Desmosomal junctions between interdigitating processes of two adjacent keratinocytes
Adjacent cells
* Two adjacent cells will project cytoplasmic processes towards each other
* Attach via desmosomes (macula adherens)
* If there were no desmosomal attachments...
* Fissures in the skin would form due to injury
* This would cause the body to be vulnerable to microorganisms (bacteria, viruses)
43
Stratum granulosum
Stratum granulosum
* In thick skin, granulosum contains _3 or 4 layers_
* Cells here have _nuclei_ but they are fragmented
* DNA is breaking down
* Cells appear apoptotic
* Cells have many _granules_
* Keratohyalin granules (protein, contain keratohalin)
* Membrane coating granules (lipid)
44
Membrane-coating granules of the stratum granulosum
Membrane-coating granules
* Relsease lipid into the extracellular space
* Lipid forms sheet of waterproof material
* Good for sheilding the body from water gain/loss
* But the lipids also impede diffusion of nutrients and oxygen, causing cell death beyond this layer
45
Stratum lucidum
Stratum lucidum
* Allows light to pass through - it is the light staining layer
* Not very visible in micrographs of thin skin
* It is a sublayer of the stratum coreum
* Contains ONLY dead cellular material
* There are NO cytoplasms or organelles present
46
Stratum Corneum
Stratum corneum
* Very thick in the thick skin
* Recall that the thickest skin is found in the soles of our feet and also to a lesser extend in the palms of our hands
* This is a lyer of DEAD cellular material
* Lots of _keratin_ is found here (protective material)
47
Strata of thin skin
Thin skin contains...
* **Stratum corneum** (thin)
* There is an absence of a definitive _stratum lucidum_, however individual cells are present
* There is also an absense of a definitive _stratum granulosum_, hoever individual cells are present
* **Stratum spinosum**
* **Stratum basale**
48
Ichthyosis
49
Dermis
Dermis
* Connective tissue layer of the skin
* Contains two layers
* Papillary layer
* Reticular layer
50
Papillary layer of the dermis
Papillary layer
* Most superficial layer of the dermis that extends into dermal papilla
* Composed of **loose connective tissue**
* Has fibroblasts, macrophages, mast cells, plasma cells
* **Functions to protect the body from invasion by microorganisms**
51
Papillary layer of the dermis in THICK skin
Thick skin
* In areas subject to "mechanical stress" (palms and soles), you will see...
* Prominant epidermal ridges (dermal papilla)
* True dermal ridges
52
Reticular layer of the dermis
Reticular layer
* Provides tensile strength
* Thickest layer of the dermsi
* Contains collagen bundles
* Many bundles will run in different directions (look like pink ribbons)
* Prevent the skin from breaking apart
* Also contains some elastic fibers
53
What do the dome-shaped ridges of thick skin form?
Finger prints!
54
Dermis vs. Hypodermis
The hypodermis is NOT part of the skin
* Dermis contains...
* Ducts of sweat glands
* Portions of hair follicles
* Sebaceous glands
* Hypodermis: the layer _underneath the dermis_
* Also known as the superficial fascia
* Contains some adipose tissue
* Again, NOT part of the skin
55
Four types of receptors found in the skin
There are four types:
1. **Free nerve endings**
* Pain and temperature receptors
2. **Pacinian corpuscle**
* Detects pressure and vibrations
3. **Meissner's corpuscle**
* Mechanoreceptors for discriminatory, fine touch
* Found in dermal papilla
4. **Krause end bulbs**
* Function is unclear
56
What are the two types of sweat glands in our body?
1. Eccrine
2. Apocrine
57
Which of the two sweat glands is the "ordinary" sweat gland found throughout the body?
Eccrine sweat glands
* Found in most of the skin
* Activated in heat and exercise
* They squirt out their products onto the skin
* Also function in the excretion or expulsion of waste product
58
What kind of cells help with expuslion in eccrine sweat glands?
* These glands have **myoepithelial cells** which assist in the "expulsion" of the **secretory product** (sweat) from the **secretory unit**
59
What type of secretory method is used in eccrine sweat glands?
* Sweat glands utilize the **merocrine** secretory method (they only secrete the product)
60
What is the innervation of eccrine sweat glands?
Innervation
* Postganglionic - sympathetic fibers
61
What type of duct does the eccrine sweat gland have?
Simple coiled tubular gland
* You will see the secretory portions lined with simple/stratified, columnar/cuboidal epithelium
* Some ducts will be made up of two layers of cuboidal epithelium
* You will see a long coiled tube
62
What type of sweat gland is specialized to have a huge lumen and is found in areas producing large amounts of sweat?
Apocrine sweat glands
* Found in the axilla, areola of the nipple, anal region
* Merocrine secretion (secretory product only)
* Innervated by the sympathetic NS
* Produce large amounts of sweat
* Sweat itself is odorless
* Bacteria on our skin breakdown products of sweat - this produces the odor
63
What do sebaceous glands produce?
Sebaceous glands are the oil producing glands of the body
* Sebaceous glands are induced by hormones and holocrine secretions
* The secretory product is know as sebum
* Empties into the hair follicle
* Cells themselves are part of the sebum
* Mature cells of the sebum become part of the secretion
64
What are the parts of a hair follicle?
Hair follicle
* Hair bulb (at base of hair) - encloses the dermal papilla
* Medulla - moderate keritinization
* Cortex - keritiniaed
* Cuticle - keritinized
* Internal root sheath - some keritinization
* External root sheat - not part of the hair (cells outside of the internal root sheath)
* Glassy membrane (like a bsement membrane)
* Connective tissue
65
Arrector pili muscle
Smooth muscle
* Attaches to the hair follicle midway and obliquely
* Functions to rais the hair
* **"Cradles" the sebaceous gland**
66
Nail plate
Nail plate
* The nail plate is a dense keratinized plate
* Rests on the nail bed (stratified squamous epithelium)
67
Nail matrix
Nail matrix
* Epithelium under nail root
* Growth occurs here
