12. The blood vessels of the heart. Conducting system (innervation) of the heart The histology of blood vessels. The formation of granulocytes (granulocytopoesis).

12. The blood vessels of the heart. Conducting system (innervation) of the heart The histology of blood vessels. The formation of granulocytes (granulocytopoesis).

Anatomy: The blood vessels of the heart. Conducting system (innervation) of the heart

Arteries and Veins of Heart:

Coronary a – arise from asc aorta @ aortic sinuses – the bulges at the most proximal part of asc aorta

• supply  the myocardium and endocardium of heart, both atria and ventricles
• filled w/ blood during ventricle diastole
• max blood flow = diastole
• min blood flow = systole

Ventricles are covered w/ epicardial fat (deep to the epicardium)
blood vessels of heart embedded into the fat on the surface of heart
so musc receive blood from outside
therefore – CLINCAL NOTE – the musc just below endocardium is most susceptible to hypoxia

Blood cannot enrich subendocardial musc from inside the heart, b/w the endothelium covering inside of the heart forms non-penetrable barrier.
*Heart wall is covered by simple squamous epith, called endothelium*

There are no anastomosis w/in subendocardial musc arteries w/ other coronary a – so if a is blocked, the area it supply simply receives no blood.

Anastomosis do exit on the surface of the heart.

1. R coronary a – emerges from R aortic sinus, and turns R to run under R auricle, then to coronary groove –> gives off marginal branch –> turns to post side of heart (still in groove) –> when reaches the middle of posterior surface = gives post Intraventricular br, which descends down the back of heart and runs to apex

Branches of R coronary a:

• SA nodal br
• R marginal a
• AV nodal br
• Post IV a

Areas supplied by R coronary a:

• SA node
• AV node
• R atrium
• R ventricle except narrow strip @ ant intraventricular septum
• the Post intraventricular septa

CLINICAL NOTE –  If nodal br to SA node blocked (whether from L or R coronary a) – will lead to arrythmia – ventricle contraction will be separated from atria = nodal delay

2. Left Coronary a – emerges from L aortic sinus, and runs L and under pulmonary trunk and then the L auricle of heart –> is shorter than right –> gives major anterior intraventricular br –> sends a branch around the coronary groove of heart as well = circumflex br & branch down the left margin of heart

Branches of L coronary a:

• circumflex a
• ant IV br (sometimes called desc br)
• L marginal a
• Lat diagonal br
• sometimes will give the nodal br of SA node

Areas supplied by L coronary a:

• L atrium
• L ventricle
• Ant IV septa
• narrow zone of R ventricle by ant IV septa

Cardiac veins: 3 major, 1 minor v, cardiac sinus

1. Great cardiac v – begins @ apex of heart –> asc in ant IV groove –> coronary sinus, runs w. it in coronary groove, turns L

2. Coronary sinus – largest vein of heart, in coronary groove b/w atria and ventricles

• opens into R atrium b/w IVC and tricuspid valve, covered by Thebesian valve
• formed from the joining of great, middle, lesser cardiac v
• Then, oblique vein of L atrium & post v of L ventricle flow into it

3. Middle cardiac v – runs from apex –> in post IV groove w/ post IV br of R coronary a

4. Lesser (small) cardiac v – originates from ant side of coronary groove, runs on R margin w/ marginal a of R coronary a

5. Oblique v of L atrium – remnant of embryonic ant cardinal v, on post wall of L atrium, runs b/w the pulmonary veins, runs in an oblique (diagonal) direction –> coronary sinus

6. Ant cardiac v – originates from wall of R ventricle, bridges over coronary groove and opens directly into R atrium
drains R ventricle itself

7. Minimae cardiac veins (venae cordis minimae) – originate in walls of the chambers themselves and drain into each chamber directly. So each chamber has a little bit of venous blood flowing into it.

Lymph Drainage of Heart covered in topic #17

Conduction System of Heart: done in order of flow of signal

1. SA node – primary pacemaker of heart

• located just deep to epicardium, @ junction of opening of SVC on crista terminalis
• collection of specialized cardiac musc fibers
• impulse = 70x a min
• Blood supply: nodal br of R or L coronary a
• Innervation: cardiac plexus
• NOTE SNS = inc heart rate (HR), PNS = dec HR

2.AV node – secondary pacemaker of heart

• located b/w tricuspid and opening of coronary sinus on intra-atrial septum
• receives signal from SA node via muscle of heart
• sends signal up walls of ventricle via AV bundles
• Blood supply = AV nodal br of  R coronary
• SNS = speeds up conduction, PNS = slows conduction

3. AV bundle – the only connection b/w the atria/ventricular myocardium conduction systems (remember that anulus fibrosus acts like an insulator b/w the two)

• runs through anulus fibrosus & moderator band
• inside inter-ventricular septum
  
• divides in R & L bundle
• same as Bundle of His, or bundles of Tawara

4. Purkinje fibers –

• are branches from R & L AV bundles
• R bundle – stimulates (+) muscle in IV septum, ant papillary musc of R ventricle via moderator band and wall of R ventricle
• L bundle – stimulates (+) IV septum, ant/post papillary musc and wall of L ventricle

Pathway of conduction:

1. SA node starts signal that conducted via cardiac m fibers in atria, causing them to contract
2. Impulse spreads via myogenic conduction that sends signal from SA node to AV node
3. Signal from AV node –> AV bundle and its branches,
4. R & L bundles –> run on each side of IV septum to supply walls of ventricles respectively and papillary m

Innervation of Heart itself:

• rec Sup,Mid,Inf cervical and thoracic cardiac n from SNS trunk and CN X plexus
• SNS = Made of the presynaptic fibers from T1-T5, and post synaptic fibers from cervical and stellate ggl of SNS trunk
• PNS =  presynaptic fibers of CN X
• have superficial and deep branches (beneath/behind arch of aorta)

• SNS = Inc HR, force of contraction –> VD of coronary a (from lat horn of T1-5)
• PNS = dec HR –> VC of coronary a (CN X)

Histology: The histology of blood vessels.

Embryology:The formation of granulocytes (granulocytopoesis).