HUBS192 - Learning objectives PDF

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First-year health science HUBS192 learning objectives covered in full detailed notes....

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Skin L1-2: Describe layers of the skin Cutaneous: Epidermis: CLGSB - Stratified barrier - Mostly keratinocytes - No circulation  avascular Stratum corneum (horny layer): dead, dried-out hard cells without nuclei Stratum granulosum (granular layer): contain granules that promote dehydration of the cell, crosslinking of keratin fibres. Waxy material is secreted into the intercellular spaces. Stratum spinosum (spiny or prickle layer): intercellular bridges called desmosomes link the cells together. The cells become increasingly flattened as they move upward. Stratum basale: Columnar (tall) regenerative cells. As the basal cell divides, a daughter cell migrates upwards to replenish layer above.  push out the replacing cells that are shared at the top (keratinocyte conveyor) Strip taping  stratum corneum layer can be completely removed Dermis: Papillary layer and reticular layer - Protein fibres for strength - Vascular (nourishes epidermis) Subcutaneous: Hypodermis: - Adipose tissue Border of dermis and epidermis, provides nourishment for epidermis  large surface area to allow the circulation of nutrients from the dermis to the epidermis. Describe the functions of the skin Epithelial tissue: - Covers exposed surfaces - Lines internal passageways and chambers - Forms secretory glands Stratified and simple squamous epithelia  Squamous, cuboidal and columnar Dermis: - Not shed - Protein fibres for strength: collagen and elastin - Vascular: nourishes epidermis Hypodermis: - Contains adipose tissue  insulation Thick skin  Thick skin only found in two places palms of hands and soles of feet - Has an extra layer called stratum lucidum - Stratum corneum horny layer that is much thicker for extra protection - No hair - Extra epidermal layer Describe the accessory structures of the skin and their function Hair: located all over the body  hair shaft, hair follicle and arrector pili muscle Sebaceous gland: - Produces sebum  natural moisturiser/water repellent - Lanolin  sheep sebum (skincare) Acne: - Blockages of hair follicles + infection

- Increased sebum increases acne risk Sweat glands: - Eccrine (everywhere  thermoregulation) - Apocrine (specialised) Situated deep in skin release into base of hair follicle  oily, Receptors: Tactile, Lamellar and Bulbous Nails: - Protect fingertips - Enhance sensation: sensory receptors require deformation How skin anatomy relates to skin aging, pigmentation, tattoo and melanoma Skin aging: - Thin epidermis/ Drier epidermis  less sebum - Thin dermis (sagging/wrinkling)  reduced collagen - Slower skin repair - Impaired cooling  less sweat (decreased perspiration) - Less pigmentation  pale skin a grey hair (fewer melanocytes) - Reduced blood supply - Fewer active follicles - Altered hair and fat distribution Skin pigmentation: melanocytes and melanosomes The melanin pigment absorbs UV light  protecting cells from UV damage - Produced in melanocytes - Transferred to epidermal cells by melanosomes  vesicles containing melanin Mole is cluster of melanocytes, whereas freckle is caused by melanocytes overproducing melanosomes Epidermal pigmentation: - Melanocytes are only found in the stratum basale (pigment does not shed) - Melanosomes are found throughout the epidermis  shed with keratinocytes - Density of melanocytes varies throughout the body (but not between races) Vitamin D deficiency  rickets Skin cancer: Basal cell carcinoma: - Common but relatively benign - Originates in stratum basale - Metastasis is rare Malignant melanoma: - Rare but deadly if not treated - Originates in melanocytes - High metastasis  mortality rate dependent upon tumour Tattoo: Artificial pigmentation deposited into the dermal layer (not shed)  captured inside immune cells/scar tissue and do not get broken down L3: Function of sensory receptors in skin Free nerve endings: most common - Unmyelinated small diameter fibres and some myelinated fibres  small swellings of sensory terminals. Sensory terminals have receptors that function as cation channels  depolarization  AP (through Na+ and Ca2+ ion channels) - Respond to: temperature, pain, movement and pressure, itch (histamine), movement of hair Tactile (merkel) discs: Nerve endings located deepest layer of epidermis

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Large disc shape cells: communication between the tactile epithelial cell and nerve ending. Detects stimuli and triggers depolarization  AP somatosensory terminal - Small receptive fields (two-point discrimination): texture, shape, edges, fine touch and light pressure Tactile corpuscles: located in papillary layer of dermis - Especially in hairless skin  finger pads, lips, eyelids, external genitalia, soles of feet and nipples - Encapsulated  spiralling/branching unmyelinated sensory terminals surrounded by modified Schwann cells and thin oval fibrous connective tissue - Deformation of capsule triggers entry of Na+ ions into nerve terminal = AP - Sense: fine discriminative touch, light pressure and low frequency vibration Lamellar corpuscles: scattered deep in dermis and hypodermis - Single dendrite lying within concentric layers of collagen fibres and specialized fibroblasts - Layers separated by gelatinous interstitial fluid - Dendrite essentially isolated from stimuli other than deep pressure - Deformation of capsule opens pressure sensitive Na+ channels in sensory axon: inner layers covering axon terminal ‘relax’ quickly so APs stop. Stimulated by deep pressure, also vibration (250Hz) Bulbous corpuscles (Ruffini’s endings): Located in dermis and subcutaneous tissue - Nerve endings intertwined with a core of collagen fibres continuous with those surrounding the dermis  capsule surround entire structure - Sensitive to sustained deep pressure and stretching or distortion of the skin  signal states of deformation over prolonged times - Found in joint capsule where help signal degree of joint rotation How skin bloodflow can be controlled Smooth muscle in walls of arteries and pre-capillary sphincters innervated by the sympathetic nervous system (SNS) - Noradrenaline acts on a1 adrenergic receptors on this vascular smooth muscle in skin: GCPRs coupled to intracellular 2nd messenger  increased intracellular Ca2+  constriction = reduced blood flow. - Reducing SNS activity therefore causes relaxation (dilation) arteries to skin  increased skin bloodflow. Important in thermoregulation and blood pressure homeostasis Structure and function of eccrine sweat glands and their role in thermoregulation Innervated by sympathetic nervous system - Sympathetic cholinergic i.e. Release Ach onto mACHRs (GPCRs) - Some eccrine sweat glands can also be stimulated by adrenaline in blood acting on beta receptors – nervous sweating on palms and soles. - Noradrenaline and adrenaline act on beta 1 receptors Basic mechanisms of heat transfer - Radiation: electromagnetic spectrum, we emit and absorb infrared radiation - Conduction: when a warm object is in contact with an object of different temperature  heat gradient is formed, and equilibrium can form. - Evaporation: when evaporating water from surface of body you are removing heat energy from body. Only method od heat loss in hot climates. - Convection: wind chill factor and water convection, as it can absorb some of our heat energy. When environmental heat > body temp  radiation, conduction and convection not effective heat loss mechanisms. Core body temperature 36.5-37.5 degrees Mechanisms for heat loss and heat conservation/generation - Preoptic area of the hypothalamus contains hot and cold sensitive neurons If blood temp goes above set point heat loss centre is activated:

- Decreased SNS activation of alpha 1 on skin blood vessels  vasodilation - Increased SNS cholinergic activation of mAChRs on sweating glands  sweating - Increased respiratory rate - Behavioural changes Central thermoreceptors detect temperature below set point which activates heat gain: - Increased generation of body heat - Non-shivering thermogenesis - Shivering thermogenesis Conservation of body heat: decreases blood flow to dermis, reducing heat loss by radiation and convection - Shivering: increased tone of skeletal muscles  due to oscillatory contractions of agonist and antagonist muscles mediated by muscle spindles (stretch receptors) - Non-shivering thermogenesis: increased sympathetic nerve activity (more circulation of adrenaline/noradrenaline from adrenal medulla)  increased cellular metabolism (glycogenolysis in liver and muscle)  uncoupling of oxidative phosphorylation  heat produced instead of ATP. - Increased thyroxine: in reponse to TRH and TSH  increased basal metabolic rate. Arrector pili muscles: Attach hair follicles to upper dermis  alpha 1 receptors - Contraction pulls hair upright an dimples skin  goosebumps - Compresses sebaceous glands which lubricate skin Basic classification of burns and complications First degree burn: superficial layer  only outer layer of the epidermis - Red/pink, dry and painful - Usually no blisters e.g. A mild sunburn - Skin remains a water and bacterial barrier - Heals 3-10 days Second degree burns: epidermis + varying amounts of dermis - Painful, moist, red and blistered - Usually heal in 1-2 weeks  need good dressings Deeper: - May include whiteish/waxy looking areas - Hair follicles, sweat glands may remain intact - Some tactile receptors may be lost  usually heal in 1 month but have scarring Third degree burns: - Full thickness: extend into subcutaneous tissue and may involve muscle or bone - Varied colour from waxy white through to deep red or black  hard/dry and leathery - No pain as sensory nerve endings destroyed - May require skin grafting  weeks to generate scarring Potential complications of severe burns: Skin function: - Dehydration and hypovolemic shock - Infection/sepsis - Hypothermia Severe burns also cause dysfunction in other systems - Electrolyte imbalances - Hypermetabolism - Gastrointestinal ulcers - Renal failure - Respiratory dysfunction L4: The general organization of cardiovascular system Organs consist of:

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Heart: pump blood to target tissues Arteries: supply  carriers of blood Veins/lymphatics: drainage  veins carry blood away from capillaries, and lymphatics carries blood that has left the vascular space back into blood vascular space. - Capillaries: exchange  little cellular tubes (thin walled) that allow exchange between blood and target tissues. Vascular tissue consists of: - Connective tissues: provide different functions e.g. elastin and collagen - Cells: epithelia and muscle  epithelia from barrier between cells and environments – smooth and cardiac muscle. Pulmonary circuit: - Receiving deoxygenated blood from the right side and pumping it to the lungs for reoxygenation  carried by arteries - Veins drain the lungs and bring reoxygenated blood back to the left side Systemic circulation: - Returns deoxygenated blood of tissues back to the left side (pulmonary circuit for reoxygenation) - Supplies tissues with oxygenated blood that has left the left side of heart. Lymph vascular network: Accumulated any fluid that has left the blood vascular system into fine capillaries  which it brings back to the right side of the heart.  pass through lymph nodes which have an immune surveillance role Orientate the heart with the thorax Supply side: - Major arteries are situated deep to avoid damage: as you can lose a lot of blood if ruptured due to high pressure  deep in trunk, on flexors aspects of limbs. - Structures often receive supply from two sources  hand and brain Exchange network: capillaries varying degrees of permeability - Continuous (controlled – tight) - Fenestrated (leaky) - Sinusoidal (very leaky) 3 pathways of drainage: - Blood vascular: deep veins (behind muscle) and superficial veins (below dermis) - Lymphatics: leaves blood vascular system - Drainage can be close to skin  CSA of veins is 2x that of arteries under smaller pressures, but supply = drainage. Mediastinum is a cavity where the heart is held flanked by the cavities  rotated left and tilted posteriorly/right ventricles toward the front - The base sits between the 2nd and 3rd rib. The chambered structure of the heart and relate this to pumping action The heart has 4 chambers: - 2 chambers associated with the right pump, supplying the pulmonary circuit. - 2 chambers associated with the left pump, supplying the systemic circuit. Right atrium (receiving chamber): receives deoxygenated blood and drains down into the ventricular chamber Right ventricle: contracts pushing the deoxygenated blood and drains down into the output artery. Left atrium: once blood goes to lungs and reoxygenated it arrives in the left atrium and drains down into the left ventricle. Left ventricle: receives oxygenated blood and contracts sending to the first artery of the systemic circuit (aorta). The right and left structures are separated by the interventricular septum  prevent any movement Right atrium:

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If vein drains from head, neck, chest and upper limb areas it will drain through the superior vena cava - If vein drains from below diaphragm, then it enters through inferior vena cava and into right atrium. - Opening of the coronary sinus: venus drainage of heart itself - Tricuspid valve sends blood into the ventricular chamber and stops it going back, can only go through the pulmonary valve to the artery carrying blood to the lungs. Once blood has been reoxygenated, blood travels posterior to the heart through 2 right pulmonary veins, comes out 2 left veins into the left atrium. Ventricular contraction occurs pushing blood through aortic valve into the aorta  carries to the peripheral tissues. Understand layers of heart wall Endocardium: - Squamous endothelium  stops blood clot - Loose irregular fibrous connective tissue - Small blood vessels - Purkinje fibres Myocardium: The left ventricle is typically 3x the thickness of the right ventricle - Much shorter to right side of heart, so less force to push blood thus myocardial thickness is less. - Systemic pump on the left side of heart needs more force to push blood to peripheral tissues, greater myocardial thickness is required. Epicardium: outermost layer of heart - Visceral pericardium: contacts the heart (internal layer) - Large blood vessels - Loose irregular FCT  adipose Pericardium: sack that the heart sits in  fused to outer layer of epicardium - Non-stick/lubricated surface which allows the heart to beat - Visceral pericardium: contacts the heart (internal layer) - Parietal pericardium: external layer L5: Describe heart valves and relate to flow of blood through heart chambers AV valves: prevent blood returning to atria during ventricular contraction Right side  tricuspid valve (3 leaflets) Left side  bicuspid (mitral) valve - Filling phase of the ventricular system is called diastole  bicuspid (mitral) valves shut and AV valves open (tricuspid and semilunar) - Systole: AV valves closed  tricuspid valve shut The AV valves pushed closed by the pressure going up in the atrial chamber - When the pressure in the ventricle is higher than it is in the outflow artery, the semilunar valve opens. Allowing blood to flow out Semilunar valves: prevent blood returning to ventricles during filling phase (diastole) - Right side  pulmonary valve – 3 cusps - Left side  aortic valve – 3 cusps Pushed open as blood flows out of heart  closed as blood starts to backflow (low pressure) Diastole: - 2 big rings AV valves (diastole): open so blood must be able to flow from the atria to the ventricles. Right AV valve is tricuspid valve and left AV valve is mitral valve. - Small bottom valve: pulmonary valve - Small top valve: aortic valve Semilunar valves shut Systole: - 2 AV valves are closed

- 2 semilunar valves open Blood is being ejected from the ventricle to the outflow arteries, but not back from the ventricles to the atrial chambers. - Bicuspid (mitral) valve = 2 leaflet  left side of heart - Tricuspid (semilunar) = 3 leaflets  right side of heart Right pump = tricuspid and pulmonary pair Left pump = bicuspid and aortic pair - Papillary muscle  finger like projection attached to chordae tendineae which attach to free edge of the chords, this works to stop reflux of blood from ventricle into atrium through AV valve. AV valves are big allowing blood to pass through under low pressure Semilunar valves small as allowing blood to pass under high pressure Identify vessels of the cardiac circulation - Right coronary artery branches from the right side of aorta, that runs in the epicardium in a groove between the right atrium and right ventricle - Left coronary artery branches from the left side of aorta, down to where it branches off to the anterior interventricular artery. Another branch  which runs between the left atrium and left ventricle is the circumflex artery. Then drain blood back via cardiac veins - Right side drained by the small cardiac vein and the left side of heart drained by the great cardiac vein. They both drain back into the posterior of the heart and arrive at the coronary sinus. - Coronary sinus drains into the right atrium so it can go into the pulmonary system for reoxygenation. Compare and contrast structural features of cardiac muscle and skeletal muscle Cardiac muscle: - Long strips of capillaries, red blood cells have to travel in single file  so that the red blood cell is as close to the capillary wall, thus gas exchange is easier. Structure: - Striated - Short/branched cells  1 or occasionally 2 nuclei/cell - Central oval shape nucleus - Cytoplasmic organelles packed at the poles of nucleus - Interconnected with neighbouring cells via intercalated disks  only in cardiac muscle Intercalated disks: 1. Adhesion belts (linking actin to actin)  vertical portion: transfer of force across adhesion belts 2. Desmosomes (link cytokeratin with cytokeratin)  keeps the adhesion belts fused together 3. Gap junction (electrochemical communication)  horizontal portion: fusing of plasma between two cells allowing electrochemical communication. Electrochemically propagating contraction. Compare structure and function of cardiac muscle and purkinje cells Purkinje cells - Some peripheral myofibrils - Central nucleus, abundance of mitochondria, glycogen and lots of gap junctions - Some desmosomes and a few adhesion belts  don’t contract so not a lot of force needed - 1% of cardiac muscles L6: The major arteries and veins Arteries  supply - From the aortic bifurcation go into the common iliac arteries  which branches to from the external iliac and heads towards the lower limb  then leaves the abdominopelvic part heading down to the femoral artery  which reaches the popliteal artery behind your knee  this travels down the posterior tibial artery and finally reaches the plantar arch arteries on the sole of foot. Veins  drainage

From the plantar venous arches into the posterior tibial vein (reaches the heart  flanks artery)  reaches the popliteal vein and into the femoral vein  goes up to the external iliac vein and into the common iliac vein  finally into the inferior vena cava which drains into the right atrium. - Superficial pathway  great saphenous vein runs in the hypodermis, all the way up along the superficial path then deep into the groin. The layered structure of blood vessels Tunica intima: inner most layer - Endothelium: a simple squamous epithelium which lines the lumen of all vessels. Barrier between the blood itself and the wall, if you damage the endothelium blood in tubes will produce blood clots - Sub-endothelium: a sparse pad of loose FCT  cushioning the endothelium - Internal elastic lamina: layer of condensed elastic tissue. The IEL is well developed in arteries and less developed in veins  forms a boundary between intima and media Tunica media: - Smooth muscle - A variable content of connective tissue fibres  mainly elastin and collagen - Thickness of the media is proportional to both vessel diameter and blood pressure. Pressure = thick Tunica adventitia: - Loose FCT with a high content of collagen and variable amounts of elastin - In larger vessels, the adventitia contains the vasa vasorum  need their own blood supply, enter through the adventitia with small veins - Lymphatics and autonomic nerves are also found in this reg...