Cardiovascular

Angiotensin II

- One of the most potent vasoconstrictor agents known - Directly and indirectly (via aldosterone) enhances body salt and water retention. - Acts on cardiac muscle to cause hypertrophy -Increases the release of norepinephrine from sympathetic nerves

What are the three layers of tissue that make up an artery?

1. Tunica intima - endothelial lining continuous throughout the entire circulatory system 2. Tunica media - smooth muscle and elastic tissue layer 3. Tunica adventitia - fibrous outer coat of the vessel

Positive inotrope

A drug that enhances myocardial contractility force e.g. Pimobendan

Hepatic portal system

A modified circulatory system within systemic circulation, whereby blood is taken directly from the digestive tract to the liver so that the products can be processed immediately

Azygous vein

A vein that arises in the abdomen, runs through the heart, passing through the diaphragm and either connects with the cranial vena cava in the thorax or empties directly into the right atrium of the heart.

Ductus venosus

A venous shunt in the liver that connects the umbilical vein to the caudal vena cava, so that the oxygenated, nutrient rich blood goes straight to the fetal tissues and bypasses the liver.

Ductus arteriosus

A vessel that forms a connection between the pulmonary artery and the aorta, by passing the lungs.

What does excessive sympathetic tone promote?

Arrhythmias

What is the role of the umbilical arteries in utero?

Carries de-oxygenated blood which contains waste products from the fetus back to the placenta and so to the circulation of the dam.

What is the role of the umbilical vein in utero?

Carries oxygenated and nutrient-laden blood from the placenta to the fetus

What major veins drain blood into the right atrium?

Cranial vena cava Caudal vena cava Azygous vein

Pulmonary circulation

De-oxygenated blood is pumped from the right ventricle via the pulmonary artery to the lungs, where gas exchange between CO2 and O2 occurs. Oxygenated blood is then transported from lung capillaries to pulmonary veins which then carries the blood to the left atrium.

Right lymphatic duct

Drains lymph from the right side of the head, neck and thorax and right limb and empties into the right side of the heart via the right jugular vein or cranial vena cava

Cardiac glycosides

Drugs that are used to slow heart rate by acting to increase vagal tone and that target Na+/K+ ATPase, increasing force of cardiac contractility

Positive chronotropes

Drugs that increase heart rate e.g. atropine

Negative chronotropes

Drugs that slow the heart rate e.g. Digoxin

How does fetal circulation differ from adult circulation?

During gestation the placenta carries out the roles that will later on be performed by the lungs, kidneys, and digestive tract such as; providing oxygen and nutrients and removing waste

Which arteries branch from the aorta at its termination?

External iliac artery -> Femoral artery Internal iliac artery

Lymph flow

Flow is mainly passive and relies on the contraction of the surrounding muscles to move the lymph. There are valves present which prevent back-flow and pooling of lymph in the vessels.

Embolism

If part of a thrombus breaks off and becomes lodged in another capillary bed

What are the effects of a sustained increase in heart rate?

Increases myocardial O2 consumption Reduces time for ventricular filling (diastole) Reduces time available for coronary blood flow (diastole)

What is the route of the blood in the hepatic portal system?

It passes through two capillary beds before returning to the heart. One in the structures of the digestive tract and one in the liver. Venous blood from the liver then drains into the hepatic veins which join with the caudal vena cava.

What does the left subclavian artery supply?

It supplies the upper left limb before splitting into the left axillary artery and left brachial artery

Capillary beds

Networks of capillaries that extend between the arterioles and venules within the tissues

Foramen ovale

Opening in the septum between the right and left atria and ventricles. Blood passes from the right to left ventricle and into systemic circulation, bypassing the lungs. Closes shortly after birth.

Where does the liver get its blood supply?

Oxygenated blood from the hepatic artery Hepatic portal vein

Tracheal lymphatic ducts

Paired ducts that drain lymph from the head and neck and empty into the thoracic duct or one of the large veins near the heart.

Which arteries branch from the aorta more caudally in the thorax?

Paired spinal arteries

Veins

Relatively thin vessels that carry de-oxygenated blood towards the heart under low pressure

Cranial vena cava

Returns de-oxygenated blood from the head, neck and forelimbs to the right atrium of the heart

Caudal vena cava

Returns de-oxygenated blood from the pelvic region, hind limbs and abdominal viscera to the right atrium of the heart

Capillaries

Small, thin-walled, permeable vessels consisting of a single layer of endothelial cells

The brachiocephalic trunk

The first large artery arising from the aortic arch. It carries oxygenated blood to the head and neck through the common carotid arteries and the right forelimb via the right subclavian artery

Thoracic lymphatic duct

The main lymphatic duct, and collects blood from the rest of the body. It arises in the abdomen as the cisterna chyli, receiving lymph from the abdomen, pelvis and hindlimbs. As it enters the thorax, it becomes the thoracic duct and receives lymph from the left side of the upper body and left forelimb. It empties into either the jugular vein or cranial vena cava, just before the heart.

Thrombus

The occlusion of a vein or artery by a blood clot

Which sets of veins supply the cranial vena cava?

The paired jugular veins The paired subclavian veins

Lymphatic system

The part of the circulatory system that is responsible for returning excess tissue fluid that has leaked out of the capillaries back to the blood. It is also responsible for removing bacteria and foreign material from the lymph, and producing lymphocytes. It also transports the products of fat digestion and the fat-soluble vitamins.

Which is the only artery that carries de-oxygenated blood?

The pulmonary artery - which carries de-oxygenated blood away from the heart, to the lungs

Which is the only vein that carries oxygenated blood?

The pulmonary vein - which carries oxygenated blood from the lungs to the heart

Ligamentum arteriosus

The remnant of the ductus arteriosus that remains after its closure shortly after birth

Falciform ligament

The remnant of the ductus venosus after it closes at birth

Which arteries branch from the aorta once it is inside the abdominal cavity?

The renal arteries The ovarian and testicular arteries The coeliac artery Cranial mesenteric artery Caudal mesenteric artery

What does the right subclavian artery branch into?

The right axillary artery The right brachial artery

Venules

The smallest veins which collect de-oxygenated blood from the capillary beds

Arteries

Thick-walled vessels that carry oxygenated blood away from the heart under pressure

Lymphatic capillaries

Thin-walled, delicate tubes which form networks within the tissues. They merge to form larger lymphatic vessels

What are the main branches of the aorta?

Two coronary arteries- which supply the heart The brachiocephalic trunk The left subclavian artery

Semi-lunar valves of veins

Valves that help maintain uni-directional flow of blood in the veins, often needed because blood is working against gravity to make its way back to the heart

Negative inotrope

a drug that decreases the FORCE of heart contractions