HUBS192 Flashcards
Skin is the…
largest and most (only) visible organ of the body
What portion of body weight is skin?
16%
What surface area is skin?
1.5-2 square metres
What makes humans unique?
Our bare (not much hair), sweaty (lots of sweat glands) skin
What are the functions of skin?
Protect, excrete, maintain, produce, synthesise, store and detect
What does the skin protect?
Underlying tissues and organs against impact, abrasion, fluid loss and chemical attack
What does the skin excrete?
Salts, water and organic wastes by integumentary glands
What does the skin maintain?
Normal body temperature through either insulation or evaporative cooling as needed (thermoregulation)
What does the skin produce?
Melanin and keratin
What does melanin do?
Protect underlying tissue from ultraviolet radiation
What does keratin do?
Protect against abrasion and serves as a water repellent (hair and nails)
What does the skin synthesise?
Vitamin D3, a steroid that is subsequently converted into calcitriol, which is a hormone important to normal calcium metabolism
What does the skin store?
Lipids in adipocytes in the dermis and in adipose tissue in the subcutaneous layer
What does the skin detect?
Touch, pressure, pain, and temperature stimuli, and relay that information to the nervous system
What happens at the chemical level?
Atoms combine to form molecules
What happens at the cellular level?
Molecules interact to form cells that secrete and regulate extracellular materials and fluids
What happens at the tissue level?
Cells and extracellular materials and fluids combine to form tissues
What does epithelial tissue do?
Cover exposed surfaces, line internal passageways and chambers and form secretory glands
What does connective tissue do?
Fill internal spaces, provide structural support and store energy
What does muscle tissue do?
Contract to produce movement. Includes skeletal, cardiac and smooth muscle
What does nervous tissue do?
Conduct electrical impulses and carry information
What tissue is skin made of?
Epithelial, connective, muscle and nervous
What are the 3 layers of the skin?
Epidermis, dermis and hypodermis
What is in the cutaneous layer?
Epidermis and dermis
What is in the subcutaneous layer?
Hypodermis
What is the epidermis?
Stratified barrier, mostly keratinocytes ( cells with large amounts of keratin), no circulation (avascular)
What happens id a cut doesn’t go beyond the epidermis?
No bleeding
What is the dermis?
Protein fibres for strength and vascular (nourishes epidermis)
What is the hypodermis?
Adipose tissue- insulation
What is within the dermis?
Papillary layer and reticular layer
Describe the border between the epidermis and dermis
Has papule which increase surface area for nourishment
What are the layers of the epidermis?
Stratum corneum, Stratum lucid (in thick skin), stratum granulosum, stratum spinosum, stratum basale
What are the cells of the stratum corneum?
Dead dried out hard cells without nuclei which can be completely removed by strip-taping
What are the cells of the stratum granulosum?
Contain granules that promote dehydration of the cell, cross linking of keratin fibres. Waxy material is secreted into the intercellular spaces
What are the cells of the stratum spinosum?
Intercellular bridges called desmosomes link the cells together. The cells become increasingly flattened as they move upward
What are the cells of the stratum basal?
Columnar (tall) regenerative cells. As the basal cell divides and differentiates, a daughter cell migrates upwards to replenish layers above
What are simple epithelia?
Single layers of cells
What are the types of epithelia?
Squamous, cuboidal and columnar
What are stratified epithelia?
Multiple layers of cells
What type of epithelial cell is the epidermis?
Stratified squamous
What skin layers shed?
The epidermis and not the dermis
What protein fibres are in the dermis?
Collagen and elastin
Where is thick skin found?
Palms of hands and soles of feet
What are the characteristics of thick skin?
No hair, extra epidermal layer (stratum lucidum) for extra rigidity, stratum corneum much thicker but other layers the same
What happens to the epidermis in ageing?
Thinner and drier (less sebum and fewer active follicles)
What happens to the dermis in ageing?
Thinner (sagging and wrinkling), reduced collagen
What happens to skin repair in ageing?
Slower
What happens to cooling in ageing?
Impaired (less sweat/sweat glands)
What happens to pigmentation in ageing?
Less. Pale skin, grey hair
What is the relationship between smoking and skin ageing?
Smoking increases skin ageing
What does smoking do?
“reactive oxygen” damages collagen and elastin. vasoconstriction - nicotine increases vasopressin
Where is hair found?
All over the body (only prominent on the head) except palms of hands and soles of feet
What does hair consist of?
Hair shaft, hair follicle, arrector pili muscle and sebaceous gland
What happens when the arrector pili muscle contracts?
Causes the hair to raise
What does a sebaceous gland do?
Produce sebum which acts as a natural moisturiser/water repellent
Where is sebum produced more?
On the head, shoulders and face
What is lanolin?
Sheep sebum which is used in skincare
What is acne?
Blockage of hair follicles and infection
What does increased sebum do?
Increase the risk of acne
What are the two types of sweat glands?
Eccrine and apocrine
Where are eccrine glands?
Everywhere
What is the role of eccrine glands?
Thermoregulation
What is the role of apocrine glands?
Specialised
Where are apocrine sweat glands?
Situated deeper in the skin, release into base of the hair follicle
How are apocrine secretions described?
Oily
What are the 3 types of receptors?
Tactile, lamellar and bulbous
What receptor is deeper?
Lamellar are deeper than tactile receptors
What do nails do?
Protect fingertips and enhance sensation
What do sensory receptors require?
Deformation
What does high pigmentation do?
Protects from UV radiation
What does low pigmentation do?
Helps with vitamin D production
What does melanin pigment do?
Absorbs UV light to protect from UV damage (damage DNA)
Where is melanin produced?
In cells called melanocytes
How is melanin transported?
By melanosomes (vesicles) to the epidermal cells
Where are melanocytes found?
Only in the stratum basale
Do melanocytes shed?
No
Where are melanosomes found?
Throughout the epidermis
Do melanosomes shed?
Yes. With the keratinocytes
Where does the density of melanocytes vary?
Throughout the body but not between races
What is a mole?
Cluster of melanocytes
What causes a mole?
Overproliferation can be cause by sun exposure
What is a freckle?
Melanocytes overproducing melanosomes
What causes a freckle?
Overproduction triggered by sun exposure
What does more UV mean?
More pigment
What does less UV mean?
Less pigment
What is vitamin D deficiency?
Rickets
What is vitamin D essential for?
Normal calcium metabolism and strong bones
What does vitamin D deficiency also effect?
Mood
What is UV exposure in skin required for?
Vitamin D synthesis
Where is there a greater incidence of lightly pigmented skin?
At higher latitudes
What people are more susceptible to Vitamin D deficiency?
Highly pigmented people, particularly at extreme latitudes
What does New Zealand have one of the highest rates for worldwide?
Skin cancer
What proportion of NZers are pakeha (European descent, mostly British)?
Large proportion (74%)
What is the UV of NZ?
Intense (elliptical orbit of the sun, latitude, thin ozone)
What country also has high skin cancer rates?
Australia
What are the types of skin cancer?
Basal cell carcinoma and malignant melanoma
How is basal cell carcinoma described?
Common but relatively benign
Where does basal cell carcinoma originate?
In the stratum basale
Metastasis is ______ for basal cell carcinoma?
Rare
What is metastatis?
Breaking off and moving to and growing in another part of the body
How is Malignant melanoma described?
Rare but deadly if not treated
Where does malignant melanoma originate?
In the melanocytes (pigmented)
Malignant melanoma is ______ metastatic
Highly
What does the mortality rate of malignant melanoma depend on?
The tutor (thickness and depth as it is more likely to get into the circulatory system and cause damage to organs)
What is tattoo?
Artificial pigmentation (usually ink) deposited deep within the skin
Where is the ink of a tattoo deposited?
Into the dermal layer so it is effective and doesn’t shed
What is done with the tattoo ink?
It is captured inside the immune cells/scar tissue but not broken down
What happens to lymph nodes in tattoo?
They may become pigmented as the tattoo breaks down
What are the types of tattoo?
Trauma, decorative and cosmetic (e.g. eyebrows)
What is the Polynesian connections of tattoos?
Maori, ta moko
Samoan, Pe’a
What is meant by there is no perfect “one receptor - one function’ relationship?
Receptors can often respond to several different stimuli but will be most sensitive to a particular type
What are the types of receptors?
Free nerve endings, tactile (Merkel) discs, tactile (messier) corpuscles, lamellar (pacinian) corpuscles and bulbous corpuscles (Ruffini’s endings)
What is the most common receptors in skin?
Free nerve endings
What is the structure of free nerve endings?
Mostly unmyelinated small diameter fibres but also some small diameter myelinated fibres
Where are free nerve endings found?
Axon terminals branch into epidermis and detect lots of things
What do free nerve endings usually have?
Small swellings at distal ends called sensory terminals
What do sensory terminals have?
Receptors that function as cation channels»>depolarisation»>action potentials
What do free nerve endings respond to?
Mainly temperature (hot/cold), painful stimuli, some movement and pressure, some to itch (in response to histamine)
What do antihistamines do?
Block the receptors to the itch
What do some free nerve endings do?
Wrap around hair follicles (petririchial endings) acting as light touch receptors which detect bending of hairs
What are tactile (Merkel) discs?
Free nerve endings located in the deepest layer of the epidermis
What are tactile discs associated with?
Large disc shaped epithelial (Merkel) cells
How is communication between the tactile epithelial cell and nerve endings possible?
Via serotonin (5HT)
Where are tactile (Merkel) discs abundant?
In fingertips and they have very small receptive fields so good for two point discrimination
What are tactile (Merkel) discs sensitive to?
An objects physical features such as texture, shape and edges. Also fine touch and light pressure
Where are tactile (messier) corpuscles located?
In the papillary layers of the dermis between the epidermal ridges
Where are tactile (messier) corpuscles especially found?
In hairless skin (finger pads, lips, eyelids, soles of feet, external genitalia, nipples)
What is the structure of tactile (messier) corpuscles?
Encapsulated
Spiralling/branching unmyelinated sensory terminals surrounded by modified Schwann cells which don’t form myelin and then by a thin oval fibrous connective tissue capsule
What does deformation of the tactile (messier) corpuscle capsule trigger?
Entry of sodium ions into the nerve terminal»_space;> action potential
What do tactile (messier) corpuscles sense?
Delicate ‘fine’ or discriminative touch, light pressure and low frequency vibration (20-80Hz)
What is delicate ‘fine’ or discriminative touch?
Sensitive to shape and textural changes in exploratory touch and movement of objects over the surface of the skin
Where are lamellar (pacinian) corpuscles found?
Scattered deep in the dermis and hypodermis
What is the structure of lamellar (pacinian) corpuscles?
Single dendrite lying within concentric layers of collagen fibres (secreted by fibroblasts) and specialised fibroblasts
What are the layers of collagen fibres in lamellar (pacinian) corpuscles separated by?
Gelatinous interstitial fluid
What is the dendrite in lamellar (pacinian) corpuscles isolated from?
Stimuli other than deep pressure
What happens when there is deformation of the capsule in lamellar (pacinian) corpuscles?
Pressure sensitive sodium channels are opened in the sensory axon. Inner layers covering the axon terminal relax quickly so action potential is discontinued (rapidly adapting)
What are lamellar (pacinian) corpuscles stimulated by?
Deep pressure (when first applied) and also vibrating because rapidly adapting
What is optimal stimulation frequency?
Around 250 Hz which is similar to frequency range generated upon fingertips by textures comprising off <1 micrometre
Where are bulbous corpuscles (Ruffini’s endings) found?
In dermis and subcutaneous tissue
What is the structure of bulbous corpuscles (Ruffini’s endings) ?
Network of nerve endings intertwined with a core of collagen fibres that are continuous with those of the surrounding dermis. Capsule surrounds the entire structure
What are bulbous corpuscles (Ruffini’s endings) sensitive to?
Sustained deep pressure and stretching or distortion of the skin
What are bulbous corpuscles (Ruffini’s endings) important for?
Signalling continuous states of deformation of tissues such as heavy prolonged touch and pressure signals
Where are bulbous corpuscles (Ruffini’s endings) also found?
In joint capsules where they help signal degree of joint rotation (proprioreception)
Where are bulbous corpuscles (Ruffini’s endings) in high density?
Around fingernails so may have a role in monitoring slippage of objects across surface skin
What do bulbous corpuscles (Ruffini’s endings) allow?
Modulation of grip
Where do arteries supply blood to?
Skin in the subcutaneous layer
Where do branches of arteries go?
Extend into the superficial layers and give rise to capillary loops which supply blood to the epidermis
What happens after blood is supplied to the epidermis?
It drains down into the venous plexus
What is also in the walls of arteries/blood vessels?
Smooth muscle that is under the control of the sympathetic nervous system
What are precapillary sphincters?
Bands of smooth muscle at the start of the capillary beds. Contracting muscles constricts blood vessels and reduces blood flow to the upper layers of the skin
What does noradrenaline act on?
The alpha 1 adrenergic receptors on the vascular smooth muscle of the skin
What happens after the alpha 1 adrenergic receptors on the vascular smooth muscle of the skin?
G- protein coupled receptors (GPCR’s) coupled to intracellular 2nd messengers lead to increase intracellular calcium ions and therefore constriction. Reduces skin blood flow
What happens when SNS activity is reduced?
Relaxation (dilation) of arteries to the skin causing an increase in skin blood flow
What is skin blood flow important in?
Thermoregulation and blood pressure control
What is the optimal core body temperature/ set point?
36.5-37.5
What happens when core body temperature gets too high?
Proteins denature and problems occur
What are the mechanisms for heat transfer?
Radiation, conduction, convection and evaporation
What does radiation cause?
Heat loss in the form of infrared rays
What objects will radiate infrared rays?
Any objects not at absolute zero temperature
What radiates heat?
As well as the body radiating heat, heat rays are also being radiated from objects towards the body
What happens when the body temperature is greater than the temperature of the surroundings?
More heat will be radiated from the body than to it
What is conduction?
Transfer of heat to objects or media which are in contact
What is conduction mainly lost to?
A lot more to air than to objects
What happens when the temperature of the air beside the skin becomes equal to the temperature of the skin?
Heat will stop being lost bu conduction unless the heated air moves away to be replace by cooler air (air convection)
What is convection?
Transfer of heat to air (or water) by conduction followed by the movement of air (or water) away from the skin which maintains the heat gradient for heat loss from the body
Why does a small amount of convection almost always occur?
Because of the tendency of heated air surrounding the body to rise
When does convection increase?
In wind/ running
What happens when water evaporates from the body?
The heat energy required to cause the water to evaporate is also lost
What happens when not sweating?
Water is still evaporated from the skin and respiratory tract
When is evaporation important?
When the temperature of the environment is greater than body temperature because it is the only method that heat can be lost by
Heat loss to water vs air
The body loses heat to water faster than air
What are the eccrine sweat glands innervated by?
The sympathetic nervous system
What do sympathetic cholinergenic nerves do?
Release ACH onto mAChR’s (GPCR’s)
What can some eccrine sweat glands do?
Be stimulated by adrenaline in the blood acting on beta receptors - ‘nervous sweating’ especially on palms and soles
What is involved in temperature regulation?
The preoptic area of the hypothalamus contains heat and cold sensitive neurons (central thermoreceptors)
What happens when body temperature increases?
If blood goes above the set point then the heat loss centre is activated
What happens when the heat loss centre is activated?
- decreased SNS activation of alpha 1 receptors on skin blood vessels causes vasodilation
- increased SNS cholinergic activation of mAChR’s on sweat glands causes sweating
- Increased respiratory rate (evaporative heat loss increases)
- behavioural changes
What happens when body temperature falls?
When blood goes below the set point the heat gain centre is activated
What happens when the heat gain centre is activated?
Blood vessels vasoconstrictor to make less blood go to the skin and lose less heat to the environment. Also countercurrent exchange
What is countercurrent exchange?
Cold blood coming back in veins which are in close proximity with arteries is warmed up by heat transfer from the arteries before it reaches the surface
What are the heat generating mechanisms?
Shivering, non-shivering thermogenesis and increased thyroxine
What is shivering?
Increased tone of skeletal muscles
What happens when tone rises above a critical level?
Shivering begins due to oscillatory contractions of agonist and antagonist muscles mediated by muscles spindles (stretch receptors)
What happens in non-shivering thermogenesis?
Increased sympathetic nerve activity and increased circulating adrenaline/noradrenaline from the adrenal medulla
What happens to the metabolism in non-shivering thermogenesis?
Increased cellular metabolism/metabolic rate
What also happens in non-shivering thermogenesis (particularly in infants)?
uncoupling of oxidative phosphorylation - heat produced instead of ATP (occurs in brown fat, particularly in infants)
What is increased thyroxine in response to?
TRH and TSH
What does increase thyroxine do?
Increases the basal metabolic rate
How long will it take for increased thyroxine take to begin in adult humans?
It may take several weeks of cold before the thyroid reaches new levels of thyroxine secretion
What are arrector pili muscles?
Smooth muscle innervated by SNS (alpha 1 receptors)
What do arrector pili muscles attach to?
The hair follicle and the upper dermis
What happens when arrector pili muscles contract?
The hair is pulled upright and the skin is dimpled where it attaches to the dermis (goosebumps). Also compresses sebaceous glands which lubricates the skin
What happens if you are a hairy mammal?
Goosebumps can trap a warm layer of air around the skin and make you look bigger, scarier and more formidable but it isn’t that useful for humans but can be a good example of physiological feedforward
Where are first degree burns?
Superficial - only involve outer layers of the epidermis
What is the appearance of first degree burns?
Red/pink, dry, painful, usually no blisters
What is an example of first degree burns?
Mild sunburn
What happens to the skin in first degree burns?
Remains a water and bacterial barrier
How long does it take for first degree burns to heal?
Usually 3-10 days
Where are second degree burns?
The epidermis and varying amounts of the dermis
What is the appearance of second degree burns?
Painful, moist, red and blistered
How long does it take second degree burns to heal?
Approximately 1-2 weeks
What do second degree burns need?
Good dressings (absorptive initially)
What do deeper second degree burns look like?
May include whiteish, waxy looking areas
What happens to the hair follicles and sweat glands in deeper second degree burns?
The may remain intact
What may happen to receptors in deeper second degree burns?
Some tactile receptors may be lost meaning they are less painful
How long does it take for deeper second degree burns to heal?
Usually heal in 1 month but may have some loss of sensation and scarring
Where are third degree burns?
Full thickness - extend into subcutaneous tissue and may include muscle and bone
What is the appearance of third degree burns?
Varied colour from waxy white through to deep red or black. Hard, dry and leathery
What is the pain like in third degree burns?
There is no pain because sensory nerve endings are destroyed
What happens if third degree burns are more than a few centimetres?
They may require skin grafting
How long do third degree burns take to heal?
Weeks to regenerate and scarring
What must we know to find fluid replacement for burns?
The percentage of the total body surface area involved in second degree burns or more
What percentage is the adult head?
9%
What percentage are the upper limbs of adults?
9% each
What percentage is the adult trunk?
36% (front and back)
What percentage is the adult genitalia?
1%
What percentage is the adult lower limb?
18% each
What percentage is the child head?
15%
What percentage is the child trunk?
32% (front and back)
What percentage is the child upper limb?
9% each
What percentage is the child genitalia?
1%
What percentage is the child lower limb?
17% each
What are complications of severe burns which directly relate to the skin function?
Dehydration and hypovolemic shock, infection/sepsis and hypothermia
What are complications of severe burns which don’t relate to skin function?
electrolytes imbalances, hyper metabolism, gastrointestinal ulceration, renal failure and respiratory dysfunction
What is the cardiovascular system made up of?
Organs
What organs is the cardiovascular system made up of?
The heart, arteries, veins/lymphatics and capillaries
What is the role of the heart?
Pump
What is the role of the arteries?
Supply
What is the role of the veins/lymphatics?
Drainage
What is the role of the capillaries?
Exchange
What are the organs made up of?
Vascular tissue
What is vascular tissue made up of?
Connective tissues and cells
What do the cells consist of?
Epithelia and muscle
What do veins do?
Carry blood away from the capillaries
What do capillaries do?
They are thin and exchange nutrients and gases in the blood to the target tissues
What systems make up the cardiovascular system?
The blood vascular system and the lymphatic (vascular) system
How is the blood vascular system described?
A closed supply and drainage system (continuous loop)
How is the lymphatic (vascular) system described?
An open entry drainage system (one way)
What are the two circulations in the blood and lymph vascular systems?
The pulmonary circulation and the systemic circulation
What happens in the pulmonary circulation?
The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs for reoxygenation
What happens in the systemic circulation?
The left side of the heart receives oxygenated blood from the lungs and pumps it to the rest of the body
What happens with lymph?
Lymph which has left the capillaries and accumulated goes into the lymphatics and is returned to the vascular system. It passes lymph nodes which air present for immune surveillance
What is the supply path?
Arteries only
Where are major arteries situated?
To avoid damage (deep in the trunk, on flexor aspects of the limbs)
What do important structures often receive?
Supply from two sources - two separate arteries (hands and brain)
When do arteries change their name?
At each major branch
What is found in the exchange network?
Capillaries of varying degrees of permeability
What are the three types of capillaries?
Continuous, fenestrated and sinusoidal
How permeable are continuous capillaries?
Controlled (tight)
How permeable are fenestrated capillaries?
Leaky
How permeable are sinusoidal capillaries?
Very leaky
What are the 3 pathways for drainage?
Deep veins, superficial veins and lymphatics
What do deep veins typically have the same name as?
Arteries beside them
Where are superficial veins found?
Just below the dermis
How do veins pump blood?
At low pressure and low velocity
How do arteries pump blood?
At high pressure and high velocity
How does the cross-sectional area of veins and arteries compare?
The cross-sectional area of veins is at least twice that of arteries
Why is the cross-sectional area of veins twice arteries?
So the same volume of blood can be shifted per second. Supply = drainage
What is the shape of the heart?
It is a blunt, cone shaped organ
What is at the inferior end of the heart?
The apex
How is the apex described?
Pointed
What is at the superior end of the heart?
The base
How is the base described?
Broad
What does the heart sit in?
The mediastinum
How is the heart positioned?
It is rotated to the left and the base tilted posteriorly to bring the right side of the heart to the anterior and the left side of the heart posterior
How much of the heart sits to the left of the midline?
Two thirds
Where is the base of the heart positioned?
Between ribs 2 and 3
Where does a line from the middle of the clavicle (midclavicular line) reach?
The apex between ribs 5 and 6
Where can the point of maximal impulse (PMI)/apex beat be measured?
Where the midclavicular line meets the apex
What is the size of the heart?
Approximately the same as a closed fist
What does the superior vena cava do?
Brings deoxygenated blood from the head, neck, chest and upper limbs to the right atrium
What does the inferior vena cava do?
Bring deoxygenated blood from everywhere below the diaphragm to the right atrium
What enters the right atrium through the coronary sinus?
Venous blood from drainage of the heart
What do valves do?
Stop blood travelling backwards and insure unidirectional flow
How many pulmonary veins are there?
4 (2 left and 2 right)
What do the pulmonary veins do?
Bring oxygenated blood from the lungs to the left atrium
What are atria?
Thin walled receiving chambers
What does each side of the heart have?
An atrium and a ventricle
What are the methods of entry into the right atrium?
Superior vena cava, inferior vena cava and coronary sinus
What valve is between the right atrium and ventricle?
Tricuspid valve
What is between the right and left ventricles?
The inter ventricular septum
What is the first blood vessel in the systemic circulation?
The aorta
What valve is between the left ventricle and the aorta?
The aortic (semilunar) valve
What are the layers of the heart?
Endocardium, myocardium and epicardium + pericardium
What is the endocardium?
The layer within the heart
What is the myocardium?
The muscle within the heart
What is the epicardium?
The layer upon the heart
What is the pericardium?
The sac the heart sits in for pumping without damage
What makes up most of the heart walls thickness?
The myocardium
What part of the endocardium lines the border with the heart chamber?
The squamous epithelium (endothelium)
What does the squamous epithelium (endothelium) do?
It is thin flat cells which forms exchange surfaces and prevents blood clotting
What is also in the endocardium?
Loose irregular fibrous connective tissue (FCT), small blood vessels and purkinje fibres
What does the loose fibrous connective tissue (FCT) do in the endocardium?
Support the endothelium
What is the thickness of the left ventricle?
1.5cm
What is the thickness of the right ventricle?
0.5cm
Why is the right ventricle much thinner than the left ventricle?
Because it is a much shorter journey to the lungs than to the rest of the body
What does the left ventricle need to do?
Produce more force which requires more muscle (myocardium)
The volume of blood pumped from each ventricle is…
still the same per contraction
What makes up the epicardium?
The visceral pericardium which is at the border of the pericardial space, large blood vessels and loose irregular FCT (adipose)
What does the pericardium provide?
A protective layer
The pericardium is …
non-stick for pumping without damage
Where is the visceral layer of the pericardium?
Touching the heart
Where is the parietal layer of the pericardium?
Outside
What is between the visceral and parietal layers of the pericardium?
The pericardial space which has fluid within it for lubrication
What is the pericardium described as?
A serous membrane (continuous)
What does the pericardium consist of?
Fibrous pericardium, parietal layer, pericardial cavity and visceral layer
What is the visceral layer part of?
The pericardium and the heart wall
What valves does each side of the heart have?
A semilunar valve and an atrioventricular valve
Where is the atrioventricular valve found?
Between the atrium and the ventricle
Where is the semilunar valve found?
Between the ventricle and the outflow artery
What is the function of atrioventricular valves?
To prevent blood returning to the atria during ventricular contraction
What is the AV valve on the right side?
The tricuspid valve
How many leaflets/cusps does the tricuspid valve have?
3
What is the AV valve on the left side?
The bicuspid (mitral) valve
How many leaflets/cusps does the bicuspid valve have?
2
What is the filling phase called?
Diastole
What is the squeezing phase called?
(ventricular) systole
How is theAV valve during diastole?
Open to allow blood to drain into the ventricle
How is the semilunar valve during diastole?
Closed to prevent blood from leaving the ventricle
How is the AV valve in (ventricular) systole?
Closed to prevent blood flowing back into the atrium
How is the semilunar valve during (ventricular) systole?
Open to allow blood to exit the ventricle
What is the function of semilunar valves?
To prevent blood returning to ventricles during filling (diastole)
What is the semilunar valve on the right side?
The pulmonary (semilunar) valve
How many cusps does the pulmonary (semilunar) valve have?
3
What does the pulmonary (semilunar) valve control?
Flow into the pulmonary circulation
What is the semilunar valve on the left side?
The aortic (semilunar) valve
How many cusps does the aortic (semilunar) valve have?
3
What does the aortic (semilunar) valve control?
Flow from the left ventricle to the aorta
When are semilunar valves pushed open?
As blood flows out of the heart
When do semilunar valves close?
As the blood starts to backflow
What is the size comparison of AV and semilunar valves?
Semilunar valves are much smaller than AV valves
How is the AV leaflet described?
Large and flappy
What would the AV leaflet do if there was nothing preventing it shutting?
It would slam shut
What are papillary muscles?
Finger-like projections of the ventricular wall
What do papillary muscles do?
Tension early in systole
What are chordous tendineae?
Tendonous chords which are attached to the tip of the papillary muscle and the AV leaflet
Where is the tension in the papillary muscle transferred to?
The chord tneidneae
What do the papillary muscles and chordous tendineae do?
Allow the AV leaflet to slowly move into place when closing
Where does the first branch of the systemic circulation form the aorta go?
Straight to the heart (oxygenated blood)
Where is the right coronary artery found?
Running in a groove in the epicardium between the right atrium and ventricle (oxygenated blood)
Where does the left coronary artery run?
It runs a small distance and then branches into the circumflex artery and anterior inter ventricular artery (oxygenated blood)
What is the right side of the heart drained by?
The small cardiac vein (deoxygenated blood)
What is the left side of the heart drained by?
The great cardiac vein (deoxygenated blood)
Where do the small cardiac vein and great cardiac vein join?
At the coronary sinus at the posterior of the heart
What does the coronary sinus do?
Drain deoxygenated blood into the right atrium
What is the width of a capillary?
About the width of a red blood cell so the distance for diffusing substances to travel is minimised
What features does cardiac muscle have?
It has features of smooth and skeletal muscle as well as cardiac muscle specific specialisations
What is the function of cardiac muscle?
Beating of the heart
Is cardiac muscle striated?
Yes, just like skeletal muscle but not smooth muscle
How are the cells of cardiac muscle described?
Short, branced
How wide are cardiac muscle cells?
Approximately 25 micrometres
How many nuclei in cardiac muscle cells?
One (or occasionally 2) which is the same as smooth muscle but not skeletal
How is the nucleus in cardiac muscle described?
Centrally positioned and oval shaped (in skeletal muscle the nucleus is pushed to the outsides)
Where are cytoplasmic organelles in cardiac muscle?
Packed at the poles of the nucleus
How are cardiac muscle cells connected?
By intercalated discs which are only found in cardiac muscle
What volume of a cardiac muscle cell is mitochondria?
20%
How are the sarcomeres arranged in cardiac muscle?
Irregular and branched (not linearly arranged as in skeletal)
What are intercalated discs?
Regions between cardiomyocytes (cardiac muscle cells)
What are the 3 junctions in intercalated discs?
Adhesion belts, desmosomes and gap junctions
What do adhesion belts link?
Actin to actin via trasnmembrane proteins
Where are adhesion belts found?
In the vertical portion and transfer force between cells
What do desmosomes link?
Cytokeratin with cytokeratin
What do gap junctions allow?
Electrochemical communication
Where are gap junctions placed?
Parallel to the force of contraction because they are delicate junctions
What does the conduction system of the heart actions do?
Greatly increase the efficiency of heart pumping
What is the conduction system of the heart responsible for?
The co-ordination of heart contraction and atrioventricular valve action
What alters the rate of conduction impulse generation?
Autonomic nerves
What type of tissue is the conduction system of the heart?
Modified cardiac tissue, not nervous tissue
Where does the conduction pathway of the heart begin?
At the superior aspect of the right atrium where there is a cluster of cells called the sinoatrial node
Where does the conduction pathway go after the sinoatrial node?
Through the atrial chamber by internodal pathways
Where do the internodal pathways reunite?
At the AV node which is the gateway into the ventricular chambers
What comes after the AV node?
The AV bundle which goes down the inter ventricular septum into the tight snd left bundle branches
What is the last part of the conduction system?
Purkinje fibres
Where do purkinje fibres go?
They run up into the papillary muscles
What do purkinje cells have?
Some peripheral myofibrils, mitochondria and glycogen
Where is the nucleus of purkinje cells?
Central
What junctions are found in purkinje cells?
Lots of gap junctions because involved in communication, some desmosomes and a few adhesion belts
What portion of cardiac cells are purkinje cells?
1%
What is the first artery in the pathway from the heart to the foot?
Ascending aorta
What is after the ascending aorta?
Aortic arch
What is after the aortic arch?
Descending aorta
What is after the descending aorta?
Abdominal aorta
What is after the abdominal aorta?
Common iliac artery
What is after the common iliac artery?
External iliac artery
What is after the external iliac artery?
Femoral artery
What is after the femoral artery?
Popliteal artery
What is after the popliteal artery?
Posterior tibial artery
What is after the posterior tibial artery?
Plantar arch
What arteries are in the thoracic cavity?
Ascending aorta, aortic arch and descending artery
What arteries are in the abdominal cavity?
abdominal aorta, common iliac artery and external iliac artery
Where is the popliteal artery sitting?
Posterior to the knee
Where are the supply paths found?
Deep
What is the first vein in the path from the foot to the heart?
Plantar venous arch
What is after the plantar venous arch?
Posterior tibial vein
What is after the posterior tibial vein?
Popliteal vein
What is after the popliteal vein?
Femoral vein
What is after the femoral vein?
External iliac vein
What is after the external iliac vein?
Common iliac vein
What is after the common iliac vein?
Inferior vena cava
Where may drainage paths be found?
Deep and superficial
What vein sits superficially?
Great saphenous vein
Where is the great saphenous vein found?
Running the length of the leg in the hypodermis
What is the longest vein in the body?
The great saphenous vein
Where does the great saphenous vein join the femoral vein?
At the groin
How many layers are in blood vessels?
3
What are the 3 layers of blood vessels?
Tunica intima, tunica media and tunica adventitia
What is the inner layer of blood vessels?
Tunica intima
What is the middle layer of blood vessels?
Tunica media
What is the outer layer of blood vessels?
Tunica adventitia
What are the layers of the tunica intima?
Endothelium, sub-endothelium and internal elastic elamin
What is the endothelium?
A simple squamous epithelium which lines the lumen of all vessels
What does the endothelium act as?
A barrier between blood and the vessel wall which prevents clotting
What is the sub-endothelium?
A sparse pad of loose FCT cushioning and supporting the endothelium
What is the internal elastic lamina?
A condensed sheet of elastic tissue.
How does the IEL compare in veins and arteries?
It is well developed in arteries and less developed in veins
What is the major component of the IEL?
smooth muscle which is under involuntary control and autonomic tone
What is the content of connective tissue in the tunica media?
Variable fibres of mainly elastin and collage
What is the thickness of the tunica media proportional to?
Vessel diameter and blood pressure - thicker in arteries than veins
What is the tunica adventitia composed of?
Loose FCT with a high content of collagen and variable amounts of elastin depending on the vessel
What does the tunica adventitia have in larger vessels?
Vasa vasorum which are blood vessels that supply the blood vessels
What is also found in the tunica adventitia?
Lymphatics and autonomic nerves
What are the two types of arteries?
Elastic arteries and muscular arteries
What do elastic arteries have?
More elastic tissue in the tunica media so that they are able to dampen the high pressure from the heart
What is an example of an elastic artery?
Thoracic artery
What do muscular arteries have?
Less elastin and more smooth muscle cells in the tunica media
What is an example of a muscular artery?
Femoral artery
What are arterioles?
Small arteries which are the last vessel in the supply path before the capillary bed
What is the function of arterioles?
Act as the resistance vessels of the circulation - determine the blood pressure
What is the function of capillaries?
Site of exchange between blood and tissues
What are venules?
The first part of the collecting (drainage) system
What do venules contain?
Monocuspid (one cusp/leaflet) valves to ensure that the blood doesn’t move backwards
What are veins?
A low pressure, large volume transport system
What do veins act to do?
Ensure one way (unidirectional) flow
What type of vessels are veins?
Capacitance vessels which can hold accumulated blood if needed.
Are capillaries capacitance vessels?
no
Are arteries capacitance vessels?
no
What is the structure of veins?
Irregular, flattened shape with large lumen and thin wall
What do veins have?
Spare capacity meaning they can take up extra blood volume
What are the layers of veins?
Intima, media and adventitia
What is the media like in veins?
Much thinner than arteries - a few layers of smooth muscle (often in two distinct layers - circumferential and longitudinal)
What is the adventitia in veins?
Often the thickest layer
Where do deep veins sit?
With skeletal muscle either side of them
What happens to deep veins when the muscle contracts?
It squeezes the vein and therefore pushes the blood up
What stops blood flowing backwards in veins?
Valves
When do varicose veins occur?
when veins dilate and so valve cusps no longer close properly allowing some blood to flow backwards
What is the function of capillaries?
Site of exchange between blood and tissues
What does the function of capillaries require?
Very thin walls, large total cross sectional area of capillary bed and slow and smooth blood flow
How does the total area of capillaries compare to arterioles?
Much larger which means much slower blood flow
What is found in a capillary?
Layer of endothelial cells, nucleus, red blood cells and intercellular (tight) junction
What is the size of a red blood cell?
8-10 micrometres
What is found in a capillary bed?
Terminal arteriole, precapillary sphincters, vascular shunt and post capillary venule
What is the terminal arteriole?
The end of the supply netwokk
What is included in the vascular shunt?
Metarteriole and thoroughfare channel
What is the post capillary venule?
Start of the drainage network
What are precapillary sphincters composed of?
Smooth muscle cells under involuntary control
What are precapillary sphincters able to do?
Constrict and prevent blood flowing into the capillary bed
What does the vascular shunt do?
Pushes blood straight from the supply to drainage without passing through the exchange network
What are the 3 types capillaries?
Continuous, fenestrated and sinusoidal
What are continuous capillaries?
Most widespread
What are fenestrated capillaries?
Leaky
What are sinusoidal capillaries?
Very leaky
What is the diameter of continuous capillaries?
8-10 micrometres (single file flow of RBC)
What is the most common form of capillary?
Continuous capillaries
What do continuous capillaries also have?
A surrounding basement layer of extracellular tissue produced by the endothelial cells which the substances must also pass through
what is the diameter of fenestrated capillaries?
8-10 micrometers (single file flow of RBC)
What do fenestrated capillaries have?
Porous openings called fenestrations
What is an example of fenestrated capillaries?
Glomerulus in the kidneys which filter the blood
What is the diameter of sinusoidal capillaries?
30-40 micrometres (multiple RBC flow)
What does the larger diameter of sinusoidal capillaries mean?
They are more likely to be involved in transport of nutrients and toxins rather than gases as RBC are further from the capillary wall
What are the size of the openings in sinusoidal capillaries?
Larger than fenestrations
How is the basement membrane in sinusoidal capillaries?
Incomplete
What is an example of sinusoidal capillaries?
Liver sinusoids
What are the methods of transport through capillaries?
Diffusion through membrane, movement through intercellular clefts, movement through fenestrations and transport via vesicles of caveolae
What substances diffuse through the membrane?
Lipid soluble substances
What substances move through intercellular clefts?
Water soluble substances
What substances move through fenestrations?
Water soluble substances
What substances move via vesicles or caveolae?
Large substances
How do substances move through continuous capillaries?
Diffusion through membrane, movement through intercellular clefts and transport via vesicles of caveolae
How do substances move through fenestrated and sinusoidal capillaries?
Diffusion through membrane, movement through intercellular clefts, movement through fenestrations and transport via vesicles of caveolae
What capillary doesn’t require transport through the basement membrane?
Sinusoidal
What is the lymph vascular system?
An open entry (drainage) system
What are the functions of the lymph vascular system?
Drain, filter, screen and absorb
What does the lymph vascular system drain?
Excess fluid and plasma proteins from tissues and returns them to the blood
What does the lymph vascular system filter?
Foreign material from the lymph
What does the lymph vascular system screen?
Lymph for foreign antigens and responds by releasing antibodies and activated immune cells
What does the lymph vascular system absorb?
Fat from intestine and transports it to blood
How does the lymphatic system commence?
As large, blind ending capillaries
What does the lymphatic system do from the small intestine?
A special group of lymphatic vessels called lacteals drain fat-laden lymph into a collecting vessel called the cisterna chyli
What do larger (thin wall) collecting vessels have?
Numerous valves to prevent backflow
How are lymph vessels described?
Thin walled (thinner than veins and arteries), no RBC’s and has valves
How is the body split when it comes to the lymphatic system?
The left side of the body and the right side of the body below the diaphragm are one section and the right side of the body above the diaphragm is another section
What does the lymph from the left side of the body and the right side of the body below the diaphragm do?
Enter the thoracic duct and drain into the left subclavian vein
What does the lymph from the right side of the body above the diaphragm do?
Enter the right lymphatic duct and drain into the right subclavian vein
What does the small intestine virus contain?
A lacteal which drains to the cisterna chill and then to the thoracic duct
Where are lymph nodes found?
Tend to be in clusters throughout the body but are also found separately
What are some of the nodes in the body?
cervical, axillary and inguinal
Where are cervical nodes?
In the neck
Where are axillary nodes?
In the armpit
Where are inguinal nodes?
In the groin
What is found in the structure of a lymph node?
Afferent lymphatics, efferent lymphatics and lymphoid cells
