Located within the mediastinum laying obliquely on top of the diaphragm and anchored to the diaphragm by the pericardium. Anterior to the esophagus and the trachea.

2/3 of the heart's mass lies on the left hand side. Has a cone shape and is about the size of a fist.

A loosely fitting membrane that encloses the heart. Funtions:

1. A protective covering for the heart

2. helps to reduce friction within the chest cavity

3. anchors the heart to the diaphragm to prevent kinking of the great vessels.

1. The outer layer- Visceral Pericardium: fibrous connective tissue layer (does not expand)

2. The inner layer- Parietal Pericardium

1) Epicardium-outermost layer or visceral pericardium

2) Myocardium- middle, thickest, muscular layer. Has intercolated discs on the muscle tissue. Branched and interconnected by the discs.

3) Endocardium- made of endothelium (lining insides of body tissues). Prevents blood from adhering to it and prevents clots from forming.

1) Right Tricuspid

2) Left Bicuspid (mitral valve)

3) Pulmonary Semilunar Valve--sends blood to the lungs

4) Aortic Semilunar Valve--sends blood to the rest of the body.

Left of the pulmonary trunk, anterior to the left atrium; fills during relaxation. Has 2 branches:

1. Circumflex branch--wraps behind; atrioventricular sulcus on the left. Decends posteriorly into the interventricular sulcus.

2. Anterior Interventricular branch--main branch, left a.d., most commonly blocked vessel in heart attacks. Supplies left and right ventricle.

Off the aorta, fills during relaxation; anterior, right off right ventricle. Has 2 branches:

1. Posterior Interventricular branch--main branch from the right coronary artery.

2. Marginal branch

Relatively hypoxic.

1) Great Cardiac Vein: Starts in the anterior interventricular sulcus, follows circumflex branch back, drains into the coronary sinus.

2) Middle Cardiac Vein: Posterior interventricular sinus to coronary sinus.

Both come together to drain into the coronary sinus.

Absolute Refractory Period: short period of time when we cannot repolarize the cell because the sodium's inactivation gate is not reset.

The function of a longer refractory period in cardiac muscle tissue is to give the heart longer periods of rest.

1) Increased number of mitochondria (aerobic response)

2) Abundant myoglobin

3) Glycogen/lipid energy stores

A) The SA Node

B) Internodal Pathways

C) The AV Node

D) The AV Bundle (Bundle of His)

E) Right and Left Bundle Branches

F) Purkinje Fibers

Initiates contraction of the entire muscle. Located at the junction of the superior vena cava and the right atrium. Is comprised of specialized nerve cells and it initiates each cardiac cycle. Two things that speed or slow: 1. Autonomic Nervous System, 2. Hormones in the nervous tissue. 

For the ANS, it is innervated by the Vagus nerve and cardioaccelorater nerves. For the hormones, epi and norepi increase force of contraction.

1. Atria must fire first to push blood into the ventricle

2. Interventricular septum fires for a stable base

3. Apex fires

4. Walls of ventricles from bottom to top

Records the electrical changes that accompany the cardiac conduction cycle. Electrodes are placed on various places on the chest wall and extremities to monitor the electrical depolarization of the cardiac muscle.

1) P wave: represents atrial depolarization--happens first

2) QRS Complex: represents ventricular depolarization--happens second. Atrial repolarization happens here but is hidden by the QRS Complex.

3) T Wave: represents ventricular repolarization

Refers to the sytole and the diastole of both atria and ventricles

1. Atria contract while ventricles relax

2. Ventricles contract while atria relax

Atria are in a relaxed state.

1) Blood is passing in passively to the right atrium. 70% of ventricular filling occurs at this time.

2) During this time, AV valves are open and SL valves are closed.

Atria are contracting, pushing blood down into the ventricles, topping off the last 30% of ventricular volume.

1) AV valves are still open and SL valves are still closed.

2) Atria are contracting; blood goes down into the ventricles and tops off the last 30% of blood volume.

3. During this time, the SA node is firing.

1) Ventricles contract, ejecting blood toward the lungs and peripheral circulation (left side)

2) AV valves close and SL valves open

1) Ventricles relax and there is a brief period of time when AV and SL valves are closed

2) AV valves eventually open back up as the pressure in the atria increases over the ventricles' pressure.

Coronary arteries are the only vessels that fill during ventricular diastole.

Sounds the valves make when they snap shut. We hear the sounds because of turbulence and turbulence creates sound.

1st heart sound: Lubb--represents the closure of the AV valves. Softer, longer sound. AKA- S1 sound

2nd heart sound: Dupp--represents the closure of the SL valves. Shorter, sharper, snapping sound. AKA- S2 sound

A) Atrial Diastole: atria relaxing and pressure steadily increases as atria fill with blood

B) Atrial Systole: atria contract, there is a momentary increase in atrial pressure as blood is sent into the ventricles to top them off.

Remember: atria are filling with blood but that blood is then travelling down to the ventricles to allow them to fill passively.

A) Ventricular diastole: 1. pressure continues to increase as blood fills the ventricle from the atria. 2. mild increase in pressure as atria contract to top off ventricular volume.

B) Ventricular systole: 1. a huge increase of ventricular pressure during ventricular contraction, 2. also see an increase pressure in the pulmonary and aorta as the ventricles contract and eject blood.

The amount of blood ejected from the L. ventricle per minute.

Stroke volume x heart rate = cardiac output

The maximum % that the cardiac output can increase above resting amounts. It is the difference between normal and maximal cardiac output.

The amount of blood pumped; difference between max and resting.

Differences can be seen in certain pathological conditions. 

In Hypovolumic Shock there is a loss of fluids. Heart rate will increase to compensate for the loss/decreasein stroke volume. Pulse will become weak.

The amount of blood left in the ventricle after ventricular systole/after contraction= 50-60mmHg.

EDV-ESV=Stroke Volume

1) Tunica Externa-aka-Adventicia: made of loose aereolar connective tissue w/ lots of collagen and elastic fibers.

2) Tunica Media: thickest layer, lots of elastic fibers w/lots of smooth muscle, oriented in concentric rings.

3) Tunica Externa-aka-Intima: made of endothelium (looks like simple squamous epithelium).

1) Pressure: stress exterted on a vessel wall as blood flows through it.

2) Resistance: a force that opposes or resists movement.

1) Pressure is directly proportional to flow rate

2) If we increase the pressure gradient, flow rate will increase as well.

3) Fluids always flow from areas of higher pressure to areas of lower pressure. 

Aorta: 100mmHg

Arteries: 100-40mmHg

Arterioles: 40-25mmHg

Capillaries: 25-12mmHg

Venules: 12-8mmHg

Veins: 10-5mmHg

Vena Cava: 2mmHg

Right Atrium: 1-0mmHg

1) Vessel diameter: the larger the diameter of the vessel, the greater the flow rate.

2) Fluid viscosity: the thickness of the fluid. Blood is 5x thicker than water => takes more pressure to push blood

3) Turbulence: can slow down blood flow; a disruption in laminar flow, creating eddies or swirls. Turbulence creates sound--a brewy is a sound you can hear on the surface of the skin.

Reported when giving a single valve for blood pressure--an average of the blood pressure for a given period of time.

MAP= diastolic + (systolic - diastolic)

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1) Increase in blood volume = increase in blood pressure

*typically doesn't happen though due to vein dilation

2) Decrease in blood volume = decrease in blood pressure

*typically doesn't happen because veins constrict to maintain homeostasis.

A) Vasomotor Center: clusters of neurons in the medulla that control vessel diameter.

1) Stimulatory VMC- causes vasoconstriction

2) Inhibitory VMC- causes vasodilation

B) Baroreceptors: responds to alterations in pressure information sent to vasomotor center.

1) Aortic Baroreceptor- monitors BP in ascending aorta

2) Carotid Sinus Baroreceptor- enlarged portion of internal carotid artery at junction of bifurcation of common carotid artery. Monitors pressure of flow to the brain through the internal carotid artery.

3) Atrial Baroreceptor- monitors pressure at the vena cava and right atrium.

C) Chemoreceptors: sensitive to chemicals in the blood (O2, CO2, pH)

*Affects the vasomotor center and respiratory centers within the brain stem to maintain homeostasis.

1) Aortic Body- located in ascending aorta

2) Carotid Body- located at the junction of internal and external carotid arteries.

D) Autonomic Nervous System Control

1) Sympathetic Stimulation- release of Epi/Norepi. Acts on centers to increase cardiac output and cause vasoconstriction of visceral vessels and vasodilation of skeletal muscle vessels.

2) Parasympathetic Stimulation- release of ACH. Decrease in cardiac output and causes vasodilation of visceral vessels and vasoconstriction of skeletal muscle vessels.

1) ADH- Antidiuretic Hormone: released by the posterior pituitary gland. Increases blood pressure when it falls too low. Aka- Argenine vasopressin. Functions 2 ways:

a) stimulates kidneys to retain H2O, preventing loss in blood volume.

b) stimulates vasoconstriction of peripheral vessels to increase blood pressure.

2) The Renin-Angiotensin-Aldosterone System: increases blood pressure.

Decreased blood flow to the kidneys => Renin release => Angiotensin (then converts to) Angiotensin I => Angoitensin II (by Angiotensin Converting Enzyme in the lungs) => Angiotensin II leads to: powerful vasoconstriction, increase in thirst, increase in ADH, increase in Aldosterone.

4) ANH (Atrial Natriuretic Hormone/Peptide): produced by specialized cardiac cells when blood pressure increases too much. Functions to lower blood pressure. Leads to:

-an increase in water loss at the kidneys

-a decrease in thirst

-blocks antidiuretic hormone and aldosterone

A) Pulmonary Circulation- functions to oxygenate blood. Unoxygenated blood leaves the pulmonary artery from the right ventricle and travels to the lungs to be oxygenated. Oxygenated blood returns to the left atrium.

B) Systemic Circulation- Carries oxygenated blood to the tissues and returns unoxygenated blood to the heart.

Ascending Aorta: largest artery. First to exit heart; its 1st branches are coronary arteries. Leads into Aortic Arch.

3 Main Branches of the Aortic Arch:

1) Brachiocephalic- 1st branch supplies R. arm and head

a) right common carotid: R. head and neck

b) right subclavian: R. upper ext. and R. upper thorax

2) L. Common Carotid- 2nd branch supplies L. side of head

3) L. Subclavian- 3rd main branch supplies L. upper ext. and L. thorax

Travel up just lateral to trachea and deep to the sternocleidomastoid muscle and split into an internal and an external carotid artery. At the level of the Hyoid bone. 

A) External Carotid: supplies blood to the head outside of the skull

B) Internal Carotid: supplies brain and tissues inside the skull. Enters skull through carotid canal.

1) Lingual: 1st branch; supplies floor of mandible

2) Facial: 2nd branch; supplies face, travels under the mandible just anterior to the angle of the jaw. Continues medially toward the medial angle of the eye. Is tortuous for jaw movement.

3) Maxiallary: 3rd branch; supplies maxillary region

4) Temporal: 4th branch; terminal branch, supplies scalp and external jaw muscles. Pulse can be taken here.

A circular blood supply within the skull that allows for collateral blood supply to the brain. Fed by internal carotids and basilar arteries. Considered an anastomosis.

Includes: the anterior cerebral artery, anterior communicating artery, middle cerebral artery, internal carotids, posterior communicating artery, posterior cerebral artery, basilar artery, and vertebral arteries.

1) Aortic arch: bends down to travel posteriorly to the heart and laterally to the vertebral column on the left side. 

2) Thoracic Aorta: no major branches (small intercostals)

3) Abdominal Aorta: has 7 main branches

1) Celiac Trunk- unilateral

a) left gastric- heads to stomach

b) hepatic- heads to liver

c) splenic- heads to spleen

2) Superior Mesenteric- unilateral, supplies pancreas, small intestines and first 2/3 of upper large intestines.

3) Suprarenals- bilateral, supply adrenal glands

4) Renals- bilateral, supply kidneys

5) Gonadal- bilateral, to testes or ovaries

6) Inferior Mesenteric- unilateral, supplies last 1/3 of large intestine, sigmoid colon, and rectum

7) Common Illiacs- bilateral, the abdominal aorta splits into these 2 main branches at the pelvis

Bilateral, split into 2 main branches:

1) Internal Iliacs: bilateral, supplies pelvic floor, urinary tract, and reproductive system.

2) External Iliacs: bilateral, travels into leg and branches into:

a) Deep Femoral: lateral to femur, wraps around leg to supply posterior lateral thigh (profunda femoris)

b) Femoral: a continuation of the ext. iliac, travels down thigh to supply posterior, anterior, and medial thigh.

Femoral artery becomes the popliteal artery as it passes behind the knee. This artery has an anastomosis with the deep femoral artery. 3 branches:

1) Anterior Tibial: supplies anterior foreleg compartment and dorsal foot to dorsalis pedis pulse.

2) Posterio Tibial: supplies posterior foreleg and plantar surface of the foot.

3) Peroneal: supplies blood to the lateral foreleg.

Prior to birth, the baby receives O2 from mother's lungs, not his/her own.

Ductus Arteriosis: the connection between the aorta and pulmonary trunk before birth. Allows blood to go straight through the aorta instead of into the pulmonary trunk. After birth, this closes and becomes the Ligamentum Arteriosum. 

Foramen Ovale: hole between the L and R atrium. Bypasses the lungs though this hole. closes and becomes the Fossa Ovalis after birth.

Ductus Venosus: a duct off of the Inf. Vena Cava that leads to the placenta. Brings blood back to the heart from the placenta. Becomes Ligamentum Teres after birth.

Umbilical Vein: leads into Ductus Venosus

Umbilical Arteries: brings blood to the placenta from the internal iliacs. 

Drains into sup. portion of body into R. atrium. Branches:

1) R. and L. Brachiocephalic Veins

*Brachiocephalics continue on as the R and L Subclavian veins at the junction of the int. and external jugular veins.

a) Ext. Jugular- bilateral, can be seen just below skin surface, drains head, neck, face, scalp, salivary glands

b) Int. Jugular- bilateral, lies inside carotid shealth w/ carotid artery and vagus nerve. Drains cranium, dural sinuses, face, and neck

2) R and L Subclavian Veins- bilateral, continue as Axillary

3) R and L Axillary Veins- continue as Brachial Veins

4) Brachial Veins- bilateral, travels up behind Humerus

1) R and L Hepatic Veins

2) R and L Suprarenal Veins

3) R and L Renal Veins

4) Gonadal Veins- bilateral

5) R and L Common Iliac Veins

6) Internal Iliac Veins

7) Femoral Veins

8) Popliteal Veins

Bilateral, drain testicular or ovarian tissue.

a) Left drains into renal vein

b) Right drains into inferior vena cava

Travel through popliteal fossa to drain into femoral veins. Has 2 branches:

1) Anterior Tibial Vein: drains anterior foreleg

2) Posterior Tibial Vein: drains posterior foreleg