CRS Flashcards
Functions of nasal cavity?
CONDUCT/PREPARE inspired air:
Warm/moisten/filter/mucous traps particles to swallow
HEAT EXCHANGERS for cooling brain: Cooled venous blood passes via rete mirabalis and cools arterial blood going to brain (warm-blooded adaptation)
OLFACTION:
Olfactory epithlium on caudal regions of turbinates
Nasal cavity landmarks?
Dorsally/laterally: facial bones
Ventrally: hard palate
Rostrally: nostrils (external nares).
Caudally: pharynx / ethmoid bone
What are Nares?
= nostrils
Actual meatus/hole
Surrounded by: hairless skin
Supported by: nasal cartilages (lateral nasal cartilage- dorsal and ventral- forms nostril opening and attached to septum)
BOVINE nostrils?
Surrounded by smooth hairless nasolabial plate
Stratified/cornified epithelium on surface
nasolabial (serous) glands create moisture
CARNIVORE nostrils?
Nasal plate: divided by median groove (philtrum)
Lateral nasal gland: secretes
SUIDAE nostrils?
Small on snout
Highly sensitive
Os rostrale: BONE- strengthens pig’s nose for digging with it
Large mucous production
AVES nostrils?
Slit openings- not diving birds
Operculum (some birds): Overhanging bony flap
Choana: allow wide communication between nasal cavity and pharynx
EQUINE nostrils?
Cartilage:
No ventral cartilage
Incomplete cartilaginous ring= distensible nostrils
Alar cartilages (plate and horn)= form comma-shaped nostrils (ventral TRUE nostril, dorsal FALSE nostril on outside- Skin lined diverticulum, within nasoincisive notch)
SEE diagram
Nostril muscles?
NOSTRIL DILATION: Levator nasolabialis Caninus Transversus nasi (Mainly important in horses) INNERVATION: Facial nerve VASCULATURE: Facial artery
NOTE: facial nerve paralysis due to innervation by SAME nerve
What is the nasal vestibule?
(Beyond nares)
= opening of nasal cavity
Contains: opening of nasolacrimal duct (connects eye to nose) on ventral surface
(DOGS) Receives: nasal gland secretions
Nasal bones?
DORSAL Frontal bones Nasal bones LATERAL Lacrimal bones Zygomatic bones Incisive bones Maxilla VENTRAL Palatine bones Maxilla Incisive bone Vomer CAUDAL Ethmoidal bone SEE diagrams
Nasal cavity position?
Cavity between: nares and cribiform plate of ethymoid bone
Rostral: nares
Caudal: Choane (paired caudal openings of nasal cavity)
SEE diagram
Nasal cavity divisions?
Divisions: INITIALLY: by nasal septum FURTHER: scrolls of turbinate bone form nasal conchae (increase SA, highly vascular structure, evolved in mammals/birds for endothermy) NOTE: The hard palate evolved at the same time (allows suckling e.g. breathing and ingesting milk) BALANCE between: Airflow resistance Defence mechanisms Warming/moistening Olfaction
Dog= complex Horse= simple (high oxygen demand)
What are nasal conchae?
Consist of turbinates covered by nasal mucosa
Scrolled up
(hollow space= reduces weight of head)
Nasal conchae shapes?
Rostral region: a.) Basal lamella Spiral lamella Recessus (coomunicates with nasal meatus) b.) Basal lamella Spiral lamella Bulla Cellulae
Caudal region:
Conchal sinus
Fusion with neighbouring bones (forms complete hollow chamber)
SEE diagram
Turbinate groups?
(Delicate scrolls) ECTOTURBINATES In frontal sinus Dogs: 6, horses: 20-30 ENDOTURBINATES In nasal cavity 5-6 1 and 2 form dorsal/middle conchae Attached to cribriform plate caudally MAXILLOTURBINATES In nasal cavity Paired Attached to maxiall medial walls Forms ventral concha
Equine turbinates?
1st endoturbinate- forms dorsal conchal sinus (conchus)
2nd endoturbinate- forms middle conchal sinus (conchus)
3rd/4th/5th grouped as ethymoidal surface
Maxillotubinate: originates from maxilla, bony support for ventral concha (contains ventral conchal sinus/conchus)
Made by different parts of turbinate bones
SEE diagram
Nasal conchae?
DORSAL concha
MIDDLE concha (horse/pig= short, dogs/ruminants= longer)
VENTRAL concha
SEE diagram
Nasal conchae divide nasal cavity into 3 separate passages: dorsal/ventral (runs into common)/middle meatus
SEE diagram
Equine meatus?
SIMPLE
4 nasal meatus: DORSAL meatus to olfactory mucosa MIDDLE meatus to paranasal sinuses VENTRAL meatus to pharynx COMMON meatus to pharynx SEE diagram
Canine turbinates?
MORE COMPLEX than equine
(Increase SA for exchange and heat control)
Large frontal sinus (not part of airflow)
Respiratory epithelium?
Pseudostratified columnar epithelium
Nasal epithelium?
VESTIBULE=
Transition from Stratified squamous epithelium (mucous membrane)
NASAL CAVITY= Respiratory epithelium
THEN caudodorsal part of ethmoidal conchae= Olfactory epithelium
NOTE: specialised region of vomer= vomeronasal organ
NOTE: Pseudostratified columnar epithelium= respiratory epithelium
Nasal epithelium?
VESTIBULE=
Transition from Stratified squamous epithelium (mucous membrane)
NASAL CAVITY= Respiratory epithelium
THEN caudodorsal part of ethmoidal conchae= Olfactory epithelium
NOTE: specialised region of vomer= vomeronasal organ NOTE: Pseudostratified columnar epithelium with cilia and goblet cells= respiratory epithelium
Nasal mucosa?
Respiratory mucosa= covers most parts of nasal cavity
Mucosa= epithelium and Lamina propria (basement membrane, contains mucous and serous glands)
Features of respiratory epithelium?
- Pseudostratified columnar
- Goblet cells (produce mucous)
- Ciliated (capture)
Observable in micrographs=
Mucous/serous glands/thin-walled veins-easily damaged
SEE diagram
Microanatomy= Top: Respiratory epithelium Middle: lamina propria (contains: capillary net, nasal glands, venous cavernous bodies, artery) Bottom: Periosteum, vein SEE diagram
Respiratory epithelium functions?
- ) Air flow regulation- by erectile tissue
- ) Cleaning- by cilia
- ) Humidification- evaporator
- ) Warming- variable blood perfusion
- ) Protection- reflex e.g. sneeze
3.) and 4.) cool brain and retain water from expiratory air in some species e.g. camels
Explain what occurs during olfaction?
Ethmoturbinates: (extend rostrally from ethmoid bone)
Covered with respiratory epithelium
Contain olfactory sensory neurones
Sniffing alters airflow: brings air into contact with ethmoturbinates
Olfactory region structure?
Olfactory regions:
Contain non-motile cilia-like structures
Specific neurones which allow exposed dendrite onto mucosal surface- detect chemicals and pass signals through to brain
Completed via cranial nerve 1 (olfactory nerve)- passes through cribiform plate (sieve-like structure at front of brain)- many holes which allow bundles of nerves (axons collect in bundles in lamina propria) from olfactory region to get to brain (olfactory lobe)
1 area of the body where neurones can regenerate (due to neural stem cells)
OVERVIEW:
Cilia-like structures detect chemicals -> pass signals back through cribiform plate via the olfactory nerve and to the brain
What is the vomeronasal organ?
= accessory olfactory sense organ
Location: contained within hard palate
paired, blind ending ducts originating from the incisive ducts, which connect nasal and oral cavities. Within these=
UNIQUE chemoreceptors:
role in pheromone detection
Lip-curling: (Flehmen in horses)- lift upper lip so air flows over vomeronasal organ to detect pheromones in air
Describe resistance to nasal airflow?
Resistance= length/radius^4 (INDIRECTIONALLY proportional i.e. ½ radius= 16x more resistance)
ALSO resistance to flow is affected by direction change
LINK: Anaesthesia- choose appropriately-sized tube (radius of tube may be too small- high resistance for animal to move gas to keep it alive)
Small changes in airway diameter makes big different in air resistance
Compromised airway in brachiocephalic dogs- narrow diameter
Turbulent= high resistance, laminar= lower resistance
EQUINE:
Obligate nasal breathers (soft palate structure makes mouth-breathing hard)
Flow aided by:
- ) Ram air into nostrils
- ) Straighter head-neck-thorax alignment
Compromise flow and air preparation
Less complex turbinates reduce resistance
Describe the paranasal sinuses?
ALL have: 1.) FRONTAL and 2.) MAXILLARY
1.) FRONTAL sinus=
Position: between nasal and cranial cavities
usually drains into ethmoidal meatus (different in HORSE)
2.) MAXILLARY sinus=
Position: caudolateral aspect of upper jaw, around cheek teeth (molars and premolars)
Species variance (e.g. horses have 2 separate regions with no communication between them)
OTHER= palatine, sphenoid, lacrimal
Describe the paranasal sinuses?
= ventilated spaces connected to nasal cavity (usually middle meatus)
ALL have: 1.) FRONTAL and 2.) MAXILLARY
1.) FRONTAL sinus=
Position: between nasal and cranial cavities
usually drains into ethmoidal meatus (different in HORSE)
2.) MAXILLARY sinus=
Position: caudolateral aspect of upper jaw, around cheek teeth (molars and premolars)
Species variance (e.g. horses have 2 separate regions with no communication between them)
OTHER= palatine, sphenoid, lacrimal CATTLE= palatomaxillary BIRDS= Infraorbital HORSES= more complex due to long skull
Development of sinuses?
7
Functions of sinuses?
Voice (resonation)
Brain insulation/cooling
Lightweight
Insertions surfaces for teeth
EQUINE paranasal sinuses (more complex):
How many sinuses does a horse have and what are they?
SEVEN Caudal maxillary sinus (and Rostral) Dorsal conchal sinus (and Ventral) Ethmoidal sinus Frontal sinus PS (Sphenopalatine sinus)
What are the cardio-respiratory functions?
TRANSPORT O2/CO2 Nutrients Heat Hormones Waste HOMEOSTASIS pH, osmolarity, etc. Infection OTHER Generate pressure (renal)
2 main features of cardiac cycle?
NOTE: usually refer to ventricles BUT also have systole/diastole
SYSTOLE (1/3 of cycle)
Ventricular contraction (CO)
LUB
DIASTOLE (2/3 of cycle)
Ventricular relaxation
(ventricles fill)
DUB
Time between lub/dub
What is the lub/dub sound generated by?
Ventricles contract-
atrioventricular valves close- flow through heart is stopped- heart/assoc. structures vibrate (NOT just valves themselves making the noise)
Time between lub dub= ventricles contracting (other time= relaxation and refilling)
Semilunar valves closing generates second heart sound
Feel pulse at same time as listening to heart: helps to identify ventricular systole
Clinical examination is VERY important (rang of what is ‘normal’ is very big)
2 main features of cardiac cycle?
NOTE: usually refer to ventricles BUT also have systole/diastole
SYSTOLE (1/3 of cycle)
Ventricular contraction (CO)
LUB
DIASTOLE (2/3 of cycle)
Ventricular relaxation
(ventricles fill)
DUB
Time between lub/dub= ventricles contracting (other time= relaxation and refilling)
Semilunar valves closing generates second heart sound
What is the lub/dub sound generated by?
Ventricles contract-
atrioventricular valves close- flow through heart is stopped- heart/assoc. structures vibrate (NOT just valves themselves making the noise)
NOTE: Feel pulse at same time as listening to heart: helps to identify ventricular systole
Clinical examination is VERY important (range of what is ‘normal’ is very big)
Function of the heart?
PUMP Cardiac output (/min) Stroke volume (/beat) Other pumping mechanisms DISTRIBUTION Unidirectional flow Constriction/dilation Vital organs Cardiac valves Vascular valves
What is stroke volume?
What is cardiac output?
SV=
end diastolic volume- end systolic volume
CO (important determinant in blood pressure)=
SV*HR
Blood pressure/flow to different organs?
Flow to different areas: determined by physiological circumstances (e.g. after eating= more flow to gut BUT less to skeletal muscles)
RENAL SYSTEM
Rely on certain perfusion pressure to function
Components of vascular system?
ARTERIES From heart VEINS To heart PORTAL VEINS Between 2 capillary beds CAPILLARIES Diffusion
Capillary bed= network of capillaries (oedema forms here when heart fails)
Heart imaging and failure?
Compensatory systems activated to maintain blood pressure if failure occurs
Angiostrongylus: ‘heart worm’ becoming more common
Radiography
Echocardiography
Avian cardiovascular system?
EFFICIENT
Metabolic demands
O2 for thermoregulation
LARGE CARDIAC SIZE (comparatively)
Large cardiac output primarily due to high heart rate
NOTE: heart size fluctuates- increase before migration (increase in athletes)
Avian cardiovascular system?
EFFICIENT
Metabolic demands
O2 for thermoregulation
LARGE CARDIAC SIZE (comparatively)
Large cardiac output primarily due to high heart rate
END OF SYSTOLE= almost completely empty
NOTE: heart size fluctuates- increase before migration (increase in athletes)
Avian cardiovascular system?
EFFICIENT
Metabolic demands
O2 for thermoregulation
LARGE CARDIAC SIZE (comparatively)
Large cardiac output primarily due to high heart rate
END OF SYSTOLE= almost completely empty
VENTRICLES=
LEFT ventricle: wall is 3x thicker, muscular bars on interior, forms entire apex
RIGHT ventricle: thin-walled
HEART LOCATION/SIZE= Comparatively large Ventral midline Enclosed by L/R liver lobes No diaphragm- pressure changes in air sacs instead
HEART STRUCTURE=
4 chambers: L/R atrium/ventricle
Valves:
NOTE: heart size fluctuates- increase before migration (increase in athletes)
Where are the valves of the heart?
Atrioventricular:
a. ) Tricuspid-
b. ) Bicuspid valve
Avian cardiovascular system?
EFFICIENT
Metabolic demands
O2 for thermoregulation
LARGE CARDIAC SIZE (comparatively)
Large cardiac output primarily due to high heart rate
END OF SYSTOLE= almost completely empty
VENTRICLES=
LEFT ventricle: wall is 3x thicker, muscular bars on interior, forms entire apex
RIGHT ventricle: thin-walled
HEART LOCATION/SIZE= Comparatively large Ventral midline Enclosed by L/R liver lobes No diaphragm- pressure changes in air sacs instead
HEART STRUCTURE=
4 chambers: L/R atrium/ventricle
Valves: Left AV valve (3 leaflets), right AV valve (muscular flap, no chordae tendinae)
RENAL PORTAL SYSTEM
NOTE: heart size fluctuates- increase before migration (increase in athletes)
Where are the valves of the heart?
Atrioventricular valves:
a. ) Tricuspid- between R atrium/R ventricle
b. ) Bicuspid (mitral) valve- between L atrium/L ventricle
Semi-lunar valves:
a. ) Aortic- left ventricle/aorta
b. ) Pulmonary- right ventricle/pulmonary artery
AVIAN cardiovascular system?
EFFICIENT
Metabolic demands
O2 for thermoregulation
LARGE CARDIAC SIZE (comparatively)
Large cardiac output primarily due to high heart rate
END OF SYSTOLE= almost completely empty
VENTRICLES=
LEFT ventricle: wall is 3x thicker, muscular bars on interior, forms entire apex
RIGHT ventricle: thin-walled
HEART LOCATION/SIZE= Comparatively large Ventral midline Enclosed by L/R liver lobes No diaphragm- pressure changes in air sacs instead
HEART STRUCTURE=
4 chambers: L/R atrium/ventricle
Valves: Left AV valve (3 leaflets), right AV valve (muscular flap, no chordae tendinae)
RENAL PORTAL SYSTEM (regulated by portal valve)
In all non-mammalian vertebrates
Receives blood from caudal body- drains hind limbs SO drugs injected into hind limbs are metabolised (go through kidneys) before general circulation (reaching veins)
NOTE: heart size fluctuates- increase before migration (increase in athletes)
FISH circulatory system?
CIRCULATION
Single circulation: gills-body-heart
HEART
Simple, linear (not divided into chambers, ventral aorta with several aortic arches)
NOTE: similar structure to developing mammalian heart
FISH circulatory system?
CIRCULATION
Single circulation: gills-body-heart
HEART
Simple, linear (not divided into chambers, ventral aorta with several aortic arches)
NOTE: similar structure to developing mammalian heart
SEE DIAGRAM OF HEART
Developing mammalian heart?
5 zones of primitive tube: SEE DIAGRAM (top to bottom) Arterial trunk/truncus arteriosus Bulbus cordis Ventricle (B and V primitive ventricle) Atrium Sinus venosus
FISH circulatory system?
Teleost
CIRCULATION Single circulation: gills-body-heart HEART Simple, linear (not divided into chambers, ventral aorta with several aortic arches) Structure: SEE DIAGRAM 1: Single dorsal aorta, runs into paired dorsal aortae, aortic arch comes off this, ventral aorta runs parallel to dorsal aorta, heart attached to dorsal aorta Flow: SEE DIAGRAM 2
NOTE: similar structure to developing mammalian heart
Developing mammalian heart?
5 zones of primitive tube: SEE DIAGRAM 3: (top to bottom) Arterial trunk/truncus arteriosus Bulbus cordis Ventricle (B and V primitive ventricle) Atrium Sinus venosus
Tetrapods
FROGS AND TOADS
Systemic arch
NOT dual-chambered BUT do have L/R aortic arch
SEE DIAGRAM 4
Anuran heart
SEE DIAGRAM 5
Frogs and toads
Fairly linear but development of valves and other structures
Recapitulation
Theory of recapitulation
Embryological parallelism
Haeckel “Ontogeny recapitulates phylogeny”
Ontogeny (the developmentof theembryofromfertilizationto gestation or hatching), goes through stages representing the stages of the evolution of the animal’s remote ancestors (phylogeny).
THEORY: Changes mammalian heart goes through represents stages of evolution
Largely discredited now BUT was supported strongly by Haeckel
Circulatory system functions?
TRANSPORT Nutrient Waste O2 and CO2 Heat Hormones PROTECTION Carries WBC and Ig HOMEOSTASIS pH, ions, fluid volume PRESSURE
Circulation of blood?
TWO PUMPS IN SERIES Pulmonary circuit: Pulmonary artery Arterioles Capillaries Pulmonary veins
Systemic circuit Aorta Arteries Arterioles Capillaries Venules Systemic veins
Circulation of blood?
TWO PUMPS IN SERIES
(If 1 side fails= serious implications on other side)
Pulmonary circuit: From bottom left to top left Pulmonary artery Arterioles Capillaries Pulmonary veins
Systemic circuit: From top right to bottom right Aorta Arteries Arterioles Capillaries Venules Systemic veins
Where are the valves of the heart?
Atrioventricular valves:
a. ) RIGHT AV= Tricuspid- between R atrium/R ventricle (3 cusps BUT often only has 2 cusps)
b. ) LEFT AV= Bicuspid (mitral) valve- between L atrium/L ventricle (2 cusps)
Semi-lunar valves:
a. ) RIGHT SEMILUNAR= Aortic- left ventricle/aorta (3 cusps)
b. ) LEFT SEMILUNAR= Pulmonic- right ventricle/pulmonary artery (3 cusps)
Chordae tendinae:
connect papillary muscles (in ventricles) to tricuspid/ bicuspid valves
Size and position of the heart across species?
How can it be accessed during surgery?
Position= essentially the same in all species
Ventral border of lungs
Laterally: lungs
Cranially: thymus
Caudally: diaphragm
In mediastinum, divides L and R pleural cavities
On midline BUT greater proportion of heart on L side
Apex= sits in sternum
Atria= Form base- dorsal (where great vessels come out)
R ventricle= cranial to L
Relatively larger in small species
Mass increases with training
Gap between lung lobes on both sides allows access to the heart (CARDIAC NOTCH)
Developing mammalian heart?
5 zones of primitive tube: SEE DIAGRAM 3: (top to bottom) Arterial trunk/truncus arteriosus Bulbus cordis Ventricle (Bulbus cordis and primitive ventricle) Atrium Sinus venosus
Primitive tube begins to ‘snap off’ into different sections
Sinus venosus doesn’t survive in mammals but does in reptiles– venous system bringing blood into primitive atria (becomes 2 atria that we know)
Bulbus cordis and primitive ventricle form the 2 ventricles
Truncus arteriosus becomes aorta and pulmonary artery
Heart structure?
Ventricles:
R= cranial to left
Paraconal groove cranially
Subsinuosal groove caudally
Atria:
Form base- blind appendages ('auricles')
Coronary groove:
Runs around heart- main trunks of coronary run in this groove3 grooves of the heart>
Coronary groove
Subsinuosal groove
Paraconal groove
Relative positions of right and left sides of the heart?
‘Fist’ analogy
Left atrium= middle/back of heart
Right ventricle wraps around front of left ventricle
What is the pericardium?
= Sac surrounding the heart- prevents distension, equlises output of 2 sides of heart Inner: VISCERAL layer of perichardium Attached to surface of heart (= epicardium) Outer: PARIETAL layer of perichardium No significant lumen Small amount of fluid in healthy animal (Contiguous with BV adventitial layer) Ligaments: Sterno-pericardial ligament Phrenico-pericardial ligament
SEE DIAGRAM 6
Right atrium:
Structure?
Position?
Features?
23-27
Left atrium:
Position?
Features?
Position:
Dorsal and caudal, under tracheal bifurcation (trachea splits into 2 main stem bronchi)
Features:
Pulmonary veins- enter in groups into 2 or 3 sites
Scar of valve of f.ovale
Right ventricle:
Structure?
Position?
Features?
Structure:
Crescentic in section
Does not go to apex of heart (left ventricle does)
Position:
Wraps around LV, cranial and to the right
Features:
Pulmonary artery- cranial and L of aorta
Trabecula septomarginalis- within R ventricle, septum- outer wall
NOTE: Trabecula septomarginalis is shown in ultrasound of heart- could be confused with pathological issue
3 grooves of the heart?
Coronary groove
Subsinuosal groove
Paraconal groove
FIBROUS cardiac skeleton functions?
Separates atria/ventricles
Insulation- AV bundle
Ruminants: ossa cordis (bone in this region for support)
Describe cardiomyocytes?
Large, cylindrical cells Striated myofibrils (LIKE skeletal) Short, branched fibres (UNLIKE skeletal) Central nuclei (UNLIKE skeletal- peripheral) Many mitochondria Actin-myosin function (LIKE skeletal)
Right atrium:
Structure?
Position?
Features?
Collects deoxygenated blood via cranial and caudal vena cava
Roof of atrium= contains intervenous tubercule- diverts blood from vena cavae to right ventricle
Sino-atrial node (in wall of R atrium)= origin of electrical activity
Coronary sinus= main blood vessel draining the heart- brings deoxygenated blood back from myochardium
Azygous vein- R or L= bring s deoxygenated blood back from other parts of the body
Fossa ovalis= remnants of interatrial foramen ovale which is open in the foetus and allows movement from R to L
SEE DIAGRAMS/GROUP OF IMAGES 12
Describe cardiomyocytes: Structure?
Function?
Training effects?
Repair?
STRUCTURE: Large, cylindrical cells Striated myofibrils (LIKE skeletal) Short, branched fibres (UNLIKE skeletal) Central nuclei (UNLIKE skeletal- peripheral) Many mitochondria Actin-myosin function (LIKE skeletal)
FUNCTION:
Excitable
Functional (electrical) syncitium
Structure facilitates fast AP passage: T-tubules, Sarcoplasmic reticulum
NOTE: Revise sarcomere structure and function
TRAINING/OVERLOAD: Myocyte hypertrophy (NOT increased cell NUMBER)
REPAIR:
Previously: thought that if damaged, cannot regenerate
BUT: increasing evidence that there are cells that lead to regeneration
Infusing stem cells into myochardium may be possibpe- particularly in human medicine (would allow myochardial regeneration which could be used for people who have suffered from a heart attack)- some interest in veterinary medicine
Explain coronary circulation?
L and R coronary arteries (L>R)
Arise from: coronary sinus (above aortic valve)
Perfusion: during ventricular diastole
Great cardiac vein- coronary sinus
How is blood pushed through the valves?
In diastole, vortexes of blood form which then pushes blood through the valves
Functions of cardiac valves?
=Generate unidirectional flow
1.) Ventricular diastole: blood enters the 2 ventricles
Most ventricular filling occurs immediately after valves open (2/3s of filling occur very quickly)
Valves start to close: atria contract to complete ventricular filling BUT contribution of atria to ventricular filling is very small- on Wigger’s diagram most of the blood in the ventricles goes in early during diastole
Atria are important in vigorous exercise in athletes- Racehorses may suffer from atrial disease
SUMMARY:
In ventricular diastole= AV valves open and blood enters 2 ventricles, semilunar valves are closed
2.) As soon as ventricular systole occurs- AV valves close but aortic/pulmonary valves don’t open until pressure in L and R ventricles exceed pressure in aorta and pulmonary artery
Once ventricular pressure exceeds aorta/pulmonary artery pressure: semilunar valves open and blood ejected into aorta/pulmonary artery
Heart begins to contract, there is a period when all 4 valves are shut- see Wigger’s diagram
3.) AS ventricles relax (at end of systole): semilunar valves shut and S2 heard
Period when all 4 valves are shut: pressure in ventricles hasn’t dropped below pressure in atrial. Once ventricular pressure drops below atrial pressure: AV valves open AND cycle begins again
NOTE: Isovolume-contraction and isovolume-relaxation should be noted on Wigger’s diagram (times when all 4 valves are shut)
FIBROUS cardiac skeleton functions?
SEE DIAGRAM 7
Separates atria/ventricles
Supports valve cusps
Cattle: sometimes bone in this region for support- ossa cordis
Insulates electrically the atria from the ventricles
Only one place for electrical activity to get from atria to ventricles= through atrioventricular node- but of wiring connects atria and ventricles (Otherwise it can not pass between the 2)
Describe the myocardoum?
Epicardium:
is the visceral pericardium (continuous with adventitial layer of blood vessels)
NOTE: Often a lot of fat associated with outside of heart
Myocardium:
bulk formed by cardiomyocytes
branches of coronary vessels supplying myocardium
Endocardium:
(lining ventricles) continuous with lining of blood vessels
SEE DIAGRAM 8
Intercalated discs
Stair-like intercellular junctions: on tread of stair= robust connections called desmosomes which stops cell tearing itself apart when muscle contracts
Gap junctions on up-side of stair which allows electrical activity to move from cell to cell
Individual cardiomyocytes BUT because of the way they’re connected, the entire myocardium tends to function as one thing- functional syncytium SO contraction occurs and electrical activity travels from cell to cell very quickly (ventricles can contract synchronously)
SEE DIAGRAM 9 AND 10 (can see this with electron microscopy) AND 11
Explain coronary circulation?
L and R coronary arteries (L>R)
Arise from: coronary sinus (above aortic valve)
Perfusion: during ventricular diastole
Great cardiac vein- coronary sinus
How is blood pushed through the valves?
In diastole, vortexes of blood form which then pushes blood through the valves
Where can you hear the different sounds of the heart?
APEX: hear first sound louder
Move up to BASE: hear second sound louder
What is the contractile function of the heart controlled by?
Electrical conduction- from cell to cell and through specialised conduction tissue
Originates from: spontaneously electrical pacemaker cells
