03 - Tissues & Integuments Flashcards
4 types of tissues
Epithelial (covering)
Muscle (movement)
Nervous (control)
Connective (support)
Where is epithelial tissue found?
- Covering & lining
eg. blood vessel
How is epithelial tissue classified?
Classified according to the number of cell layers and the shapes
- Look for where the nuclei are to determine the shape
eg. stratified squamous, simple cuboidal
Pseudostratified (Epithelial tissue classification of number of cell layers)
Not exactly layered but looks like it’s layered (looks like it has multiple layers but it is not)
- Pseudo: Kinda
Simple (Epithelial tissue classification of number of cell layers)
1 layer of cell
Stratified (Epithelial tissue classification of number of cell layers)
Multiple of layers of cells
Epithelial Tissue: avascular or vascular?
Avascular
Squamous (Epithelial tissue classification of shape)
Flattened out/pancake like
Cuboidal (Epithelial tissue classification of shape)
Cube-like
Columnar (Epithelial tissue classification of shape)
Taller than it is wide
Connective tissues functions
- Binding (eg. collagen) & support (eg. bone)
- Protection against infection (eg. blood –> WBC)
- Tissue repair
- Insulation (eg. mechanical trauma)
Why can some connective tissue repair itself?
- Most connective tissues have blood vessels running through it
- Only vascularized tissue is capable of healing itself
- Having blood vessels allow WBCs, nutrients to be delivered to deal with dead or dying cells to set the stage for healing & repair
What is the extra-cellular matrix consist of?
ECM = Ground substance + Fibers
What may be fluid, semi-fluid, gelatinous or calcified?
Ground substance
Semi-fluid –> like a gel
Gelatinous eg. cartilage
Calcified eg. bones
Give some fibers examples
eg. collagen, elastin
- Collagen means glue –> helps resist tearing when stretched
- Elastin –> this protein can be stretched but it will recoil and go back to its original shape and position
What makes connective tissues different and unique?
- Fibers give the cells their unique characteristics
- Different amounts of fiber types and cell types produce the different classes of connective tissue
Classes of Connective Tissue
- Connective tissue proper
- Cartilage
- Bone
- Blood
Types of connective tissue proper
Loose connective tissue
- Areolar
- Reticular
- Adipose (loose connective tissue)
Dense connective tissue
- Regular
- Irregular
- Elastic
Loose and dense connective tissue - how well packed are the structural fibers in the ECM
What are adipocytes?
Adipo - fat
Cytes - cells
Loose connective tissue cell
Fibroblasts adipocytes (semi-fluid ground substance)
- Loose connective tissue b/c only have a few structural fibers between them
Dense connective tissue cell
Fibroblasts (very little ground substance)
- Secreting a lot of fibers
- Immature cell
- There’s very little GS b/c the space is filled with structural proteins
- Found in eg tendons, ligaments
Cartilage cell (connective tissue)
Chondrocytes (stiff, gelatenous GS)
- Chondro - cartilage
- Cytes - cells
- Important for providing a bit of shock absorption at the end of bones (particularly when participating in an articulation eg. joint)
Characteristics of cartilage (connective tissue)
Hyaline
Fibrocartilage
Elastic
Does not repair well
Bone cell (connective tissue)
Osteocytes (calcified GS)
- Osteo - bone
- Cytes - cells
- Provides structural support
- Everything outside of the cell is Ca salts (very hard and dense)
What’s found in bone cells?
Canaliculi
Central (haversian) canal
Lacuna
Lamellae
- Will always find blood vessels running through it b/c it’s a connective tissue and a vascular tissue
Are bone cells capable of healing & repair? Why
Yes - b/c bone cells have blood vessels
Blood cell (connective tissue)
Erythrocytes/red blood cells (fluid GS)
- Erythro - red
- Cytes - cells
- Fluid GS: not just water; contains ions, glucose, clotting factors, antibodies, etc
Largest organ of the body
Skin
What is an indicator of clinical conditions and dysfunction?
The skin
What is a blue condition called? Give an example
Cyanotic
- Cyano - blue
- ic - a condition
eg. hypoxemia - low oxygen in blood
- Hypo - low
- ox - oxygen
- emia - anything related to the blood
What is a yellow condition called? Give an example
Jaundiced / Icteric
- Jaun - french for yellow
- Icteric - latin for yellow
- ic - a condition
eg. liver dysfunction (bilirubin)
- Bilirubin: recycles RBCs
Why may it be hard to notice if someone is icteric (yellow condition)?
Because they may have darker skin tones which will be hard to tell their condition
- Look for places like the sclera of the eye to see if they have a yellow condition
What is a red condition called? Give an example
Erythema
- Erythe - red
- ma - a condition
eg. heat, infection, inflammation, allergic reaction
What is a white condition called? Give an example
Pallor - less blood flowing through the integument
eg. shock (lost blood in the body thus no blood going to the skin), anemia (not making enough RBCs), peripheral vasoconstriction (when you get cold, your BVs constrict thus less blood to skin to conserve heat thus lighter skin tone)
When are pallor (white conditions) more easily noticed?
More visible in ppl with lighter skin tone
- In darker skin tones, look at the mucous membranes (eg. the gums)
What is the integumentary system consist of?
skin + accessory organs/structures (eg. nails, skin glands, hair follicles)
What is the Latin for covering?
Integumentary
How many layers are in the integumentary system? What are those layers called?
2 layers
Epidermis (superficial, thin) & dermis (deeper, thicker)
What is found in the dermis layer?
- Hair follicles
- Glands
- Sensory receptors (eg. touch, pain)
- Blood vessels
Are there BVs in epidermis layer?
Epidermis - no blood vessels
What is the dermis sitting on?
The dermis sits on the HYPODERMIS
- aka subcutaneous layer (below the cutaneous)
- The hypodermis is not part of the skin
Hypo - under
Dermo - skin
What is found in the hypodermis?
Adipocytes (loose connective tissue under the skin)
eg. fats, lipids
What are the 5 layers (strata) of the epidermis layer? From superficial to deep
Corneum
Lucidum
Granulosum
Spinosum
Basale
- Most places in the skin have 4 layers
What’s the name of the layer:
From which all other laters are derived
Basale (germinativum)
- The dividing layer
- Grows new cells (cells divide & replicate)
- Creates the cells above this layer (cells migrate up to future layers)
What’s the name of the layer:
Has 8-10 layers of cell, has keratin intermediate filaments and cells are joined by desmosomes
Spinosum (spiny)
- Keratin: structural protein (to give strength)
What’s the name of the layer:
Has 3-5 layers of cells, the transition zone (living-dead), has keratohyalin and lamellar granules
Granulosum (granular)
- Transition zone (living-dead) b/c the cells are not getting enough nutrients from the blood to stay alive
- Keratohyalin: an enzyme (helps to link the keratin filaments to one another so that they become very tough to resist being torn or stretched)
- The granules are fat containing and provide some waterproofing to this area of the epidermis
In which layer does cells start to flatten out in the epidermis?
Granulosum
What’s the name of the layer:
Only present in thick skin (eg. palm of hands, soles of feet) where there are no hair follicles
Lucidum (clear)
- Only in thick skin b/c these places has the most contact and most friction with the things in the environment
What’s the name of the layer:
Has 25-30 layers of dead cells
Corneum (horny)
- Most tough layer
- Dead keratinocytes
Why is the corneum the most tough layer in the epidermis?
To withstand abrasive forces on the epidermis
Why is the corneum the thinnest layer of epidermis when it has the most number of layers of cells?
Because those cells are all dead and flat
Where are dead skin cells found?
Dust - Half of them are dead skin cells
Truth or false
Is there a balance between cell production and cell loss (apoptosis; sloughing)?
Truth
Exactly matching rates between the production of new cells and cell loss
How long will the process of a cell from the basale to corneum strata be in the epidermis?
The entire process will take 4-6 weeks
How long will the process of a cell from basale to corneum be in psoriasis?
7-10 days
What is psoriasis?
Auto-immune disorder (immune system attacking itself)
What is an auto-immune disorder? How does the immune system work?
The adaptive immune cells identify that there’s something foreign
- The foreign protein is expressed by keratinocytes
- The foreign protein is actually self protein
This causes the WBCs to secrete a lot of chemical messengers (eg. cytokines)
- Stimulate keratinocytes to grow very quickly
Why does the surface of the skin of people with psoriasis appear as silvery scales?
The process from the basale to cornum strata is too fast which does not give the cells time to fully mature to fully make good keratin and create good interlinks between them
- The skin appears silvery scales because the skin is falling off since the cells haven’t had time to mature and develop good cell-to-cell connections
4 major cell types in the epidermis
Keratinocytes
Langerhans cell
Melanocyte
Merkel cell
What are keratinocytes?
Keratin making cells
- Dead cells
What is the predominant cell type (90%) in the epidermis?
Keratinocytes
What do keratinocytes do?
- Mainly produce keratin (a tough protein)
- Provide water shielding
- Keratin: protect from heat, abrasion, microbes, chemicals
What are Langerhans cells?
Immune cells found in the epidermis
What can langerhans cell do?
- Look for potential pathogens that may have made it across the skin due to things like an abrasion
- Macrophage - can engulf bacteria & break them down
- Macro - big
- Phage - eating
- Phagocytosis - ingestion of bacteria or other material
Where are langerhans cells found?
Stratum spinosum (only found there)
What does melanocytes do?
Produce melanin - protect us from the damaging effects of UV radiation
- They are 8% of the cells found in the epidermis layer
Where are melanocytes found?
Found in the stratum basale
Where does melanocytes deposit the melanin?
Into the stratum spinosum
Does everyone have the same amount/ratio of melanocytes?
Yes
Everyone has the same amount/ratio of melanocytes in their bodies
Where are merkel cells found?
In the stratum basale
What does merkel cells do?
Detect touch (eg. light touches) and sensations
What are merkel cells?
Specialized epithelial cell that releases neurotransmitters onto a nerve that’s in the dermis
Why can we detect light touches?
Merkel cell
- Releases neurotransmitters onto a nerve in the dermis when the cell is deformed by a light touch
- This gives us the ability to detect light touches
What are the hills & valleys made within the epidermis?
Epidermal ridges
- Gives rise to our fingerprints & footprints
0 Epidermal peg are supported by dermal papilla
Why do we have epidermal ridges?
Increases the surface area of the epidermis which improves grip
Increases contact between dermis and epidermis to prevent them from separating
What are the 2 types of melanin?
Pheomelanin - a yellow-red pigment
Eumelanin - a brown-black pigment
- Eu - good
What does melanin do?
Protection from the sun
Protects the germinal layer against damaging UV rays
What does this result in?
Increased UV = increased melanin synthesis
Tanning
What does skin colour depend on? And hair colour?
- Think of it in terms of melanin
Skin colour depends on how much melanin and which type of melanin gets made
- Everyone has the same number of melanocytes but different amounts of melanin being made
For hair colour, it is melanocytes colouring the keratinocytes
- Keratinocytes that have been modified to form single-like shapes to create a hair follicle
- Keratin is white
What determines your skin tone? What are the 3 pigments?
- Melanin (mainly)
- Carotene (vitamin A)
- Hemoglobin
What are some examples of melanocyte alterations?
Albinism - no melanin produced (the colour of keratin)
Vitiligo - loss of pigment in patches (autoimmune)
- Adaptive immune cells have identified something being foreign thus strategically attacking them in certain areas of the skin
Freckles/moles - aggregation of melanin/melanocytes
Melanoma - cancerous mole (nevus)
- Life-threatening but easy fix
ABCDE’s of malignant melanomas (life threatening)
Asymmetrical
Borders uneven
Colours (2+ colours and colour may change)
Diameter (larger than 6mm)
Elevated or Evolving
If you catch malignant melanomas early on, it is good and easy to get rid of
What does the dermis bind?
The epidermis to the underlying tissues (hypodermis)
- The hypodermis in most parts of the skin is sitting on top of some skeletal muscle attached to your skeleton
What does the dermis contain?
Collagen and elastic fibers
- Provides support for the skin
- Collagen: resists tearing
- Elastic fibers: elasticity (secreted by fibroblasts)
What’s found in the dermis?
BVs, nerves, hair follicles and skin glands
What is the dermis divided into (regions)?
Papillary region - superficial
Reticular region - deep (where most of the actions occur)
What are the types of skin glands?
- Sebaceous (oils)
- Apocrine
- Eccrine
- Ceruminous (waxy)
Sebaceous ends up on a hair follicle
Apocrine and eccrine are sweat glands (sudoriferous)
- Apocrine are found in certain regions only
- Exxrine does not go in the hair follicle
Where is the ceruminous (waxy) gland found? Why?
Ears
- Make wax to keep insects and bugs out and prevent them from laying eggs in your eggs
Where does the product of apocrine glands go?
Apocrine glands make a watery secretion (lots of proteins in it)
- The product go to the hair shaft but only in certain regions in your body
What is the arrector pili muscle?
Smooth muscle controlled by the sympathetic nervous system
- Get activated when scared (hair goes up)
- Attached to the bottom of the hair follicle and the epidermis
- Very helpful when cold (help trap a layer of air against you)
Where does the product of the eccrine gland go?
- Does not put the product in a hair follicle
- It goes right to the surface of the skin
What system is eccrine glands regulated by?
The sympathetic nervous system
- When frightened/scared, they become activated thus sweat a lot, visible perspiration on your head
What are the functions of the skin?
- Thermo-regulation
- Blood reservoir
- Protection from the environment
- Cutaneous sensations
- Excretion and absorption (minor)
- Synthesis of vitamin D
What is temperature regulation?
The maintenance of body temperature (homeostasis)
How does temp regulation work?
BVs dilate to lose heat (direct blood to the epidermis)
BVs constrict to conserve heat (direct blood away from the epidermis)
Only work because there are 2 networks of BVs in dermis
- Heat loss is also promoted by sweat production and relies on conduction & convection
What happens to temp regulation when cold? What colour will the skin appear to be?
- Constrict all BVs in the superficial BV network to get blood away from the epidermis
- Prevents heat loss
- Less blood flow to the skin thus skin will be a slightly less reddish hue
What happens to temp regulation when hot? What colour will the skin appear to be?
- May become erythematous
- Superficial reddening on the skin
- The superficial BVs and networks dilate
- Thus lots of blood are between the dermal epidermal border
- Allow the excess heat to be conducted through the epidermis and out to the air (convection)
How does the skin have the following function?
Blood reservoir
Dermis carries 8-10% of total blood volume
- In times of need(eg. bleeding out), the skin will become paler
- B/c the BVs constrict in the skin to send the blood to other more important organs (eg. heart, brain, lungs) to keep you alive
How does the skin offer protection from the environment chemically?
Chemical
- Oily secretions (sebum - set of proteins that break up the cell membrane of bacteria) containing defensins and low pH sweat (slightly acidic which keep some bacteria away), help retard the growth of microbes
- Melanin protects stem cells from damaging UV rays
How does the skin offer protection from the environment physically?
- Continuity (no breaks)
- Epidermis is a continuous layer of cells (no breaks or gaps between the cells)
- Act as a barrier to entry of pathogens into your body
- Designed to withstand abrasion (thickness of epidermis & keratin, a tough protein)
How does the skin offer protection from the environment biologically?
- Intraepidermal macrophages provide immune surveillance and help activate other immune cells
If a pathogen made past the keratocyte into your epidermis and goes down into the dermis, the macrophages will know its there and start gobbling them (also send signals to other immune cells for help)
- Leads to an inflammation
How does cutaneous sensations work?
Conveys external sensations to the spinal cord
- sensors for pain, temp, touch, pressure, etc
- A lot of skin-related sensations are conveyed to the spinal cord b/c of neurons in the dermis and some in the stratum basale of the epidermis
- Sensory receptors are located in the dermis
- In some cases, some goes up into the epidermis
How does the skin have the function of excretion and absorption?
- Waste products such as amonia and urea exreted with sweat
- A source of “insensible” H2O loss
- The amount of H2O loss has no way to capture and measure it (have to be estimated)
- Absorbs lipids, gases and organic solvents
- Anything that can pass through fat can potentially enter the skin
Sensible water loss: can be captured and measured (eg. urine)
How does metabolism in skin work?
- Contributes to the synthesis of vitamin D to maintain Ca 2+ homeostasis
- 3 organs are involved
- Synthesis of vitamin D precursor requires UV exposure (further metabolized by liver and kidney)
- Need around 15 min/day of UV radiation to get enough vitamin D
What are the 3 organs involved in the synthesis of vitamin D?
- Cholesterol (converted by UV radiation in the skin)
Go to the liver through the bloodstream
- Liver - creates another intermediate
- Kidneys - act upon the intermediate
Why does tattoos fade/blurry over time?
Tattoos fade / become blurry over time as macrophages absorb the ink particles and slowly migrate away
UV rays also damage ink particles causing fading/discolouration.
