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 (heart) 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 ventricle 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 Fossa ovalis o A depression caudal to the intervenous tubercle R Atrium o Limbus fossa ovalis – ridge marking the edge (septum secundum) Auricle Cranial ‘pouch’ that increases the volume Pectinate muscles 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 Trabeculae carneae Muscle ridges Papillary muscles – trabeculae carneae form hillocks that extend into lumen L Atrium Blood from the pulmonary vv. L Aorta 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 Bundle of His (L & R) – down the I-V wall o Trabecular Septomarginalis – to the outer wall .