Anatomy: Cardiovascular Vessels Arteries  Branching  Cross-sectional area of A + B > parent vessel  Directions o Recurrent – back in the direction of the parent vessel o Parallel o At an angle – smaller diameter = larger angle  Circumflex Vessels – a pair of vessels arising from one parent vessel and forming a loop around a bone: medial circumflex femoral a. + lateral circumflex femoral a.  End Arteries  True – blood to one structure: blockage causes an infarct (kidneys)  Functional – a potential but inadequate collateral connection exists ()

Veins  Grow larger at tributaries  Most have valves  Exceptions  Dog – angularis oculi v. + venous sinuses (skull)  Horse – buccal v. + deep facial v.  Satellite Veins – veins draining capillaries that parallel the delivering artery

Anastomoses

 Collateral Circulation – alternative pathway Arties  Works well for gradual changes

 Portal Systems – connect two capillary networks Veins  Example – portal vein: GIT  liver

 Structure – surrounded by smooth muscle cusps  Function  Relaxed = open: blood bypasses the capillaries Arteries-  Contracted = closed Veins  Example  Dermis – vasoconstriction / vasodilation  Disease – attachment of the hoof wall to the dermal lamina: open = laminitis

Blood Supply  Erectile tissue – increased arterial supply + decreased venous drainage

 Nutritional (O2) and Functional  Liver – nutritional = hepatic a., functional = portal v.  Lung – nutritional = bronchoesophageal a., functional = pulmonary a.  Sampling  Arterial – femoral a.  Venous – cephalic v. or external jugular v. The Heart  Conical with the R side twisting around the L side  Orientation  Base = cranio-dorsal, apex = caudo-ventral  The long axis is at a 45 ° angle to the back  Wall thickness – atria  R  L ventricle (3x R)

External Grooves  Coronary – between the A & V (broken on the cranial L side)  Interventricular  L / Paraconal – conus arteriosus  R / Subsinuosal – sinus venarum cavarum

Internal Features Atria and Ventricles

 Blood from the cranial VC + caudal VC + coronary sinus (great cardiac v.)  Sinus venarum cavarum  Intervenous tubercle – directs blood  o A depression caudal to the intervenous tubercle R o Limbus fossa ovalis – ridge marking the edge (septum secundum)  Auricle  Cranial ‘pouch’ that increases the volume  o All converge at the crista terminalis o Sulcus terminalis – corresponding external groove to crista terminalis

 Conus arteriosus  Curls cranially around the L side R  Terminates at the pulmonary trunk  L & R pulmonary a. Ventricle   Muscle ridges  Papillary muscles – trabeculae carneae form hillocks that extend into lumen

L Atrium Blood from the pulmonary vv.

L  arises at the centre Ventricle  Pulmonary trunk to the L and vena cava to the R

Conduction  Syncytium – Purkinje Fibres with gap junctions allow ion flow  A & V syncytia are separated by CT to prevent simultaneous contraction  Nodes  Sinoatrial – interatrial wall near the crista terminalis  A-V Node – the wall between the L & R A-V valves o (L & R) – down the I-V wall o Trabecular Septomarginalis – to the outer wall