A&P Unit E - Circulatory/Respiratory

What are the 2 parts that all blood cycles go through?

1. Pulmonary (lung) circulation

2. Systemic (body) circulation

What are the 3 types of blood vessels?

1. Arteries

2. Veins

3. Capillaries

Where is the heart located?

Located in middle of thoracic cavity - in space between lungs (mediastinum)

What are some examples of coverings of the heart?

1. Pericardium - fibrous sac containing the heart (pericardial sac, serous pericardium)

2. Pericardial space is filled w/ pericardial fluid - lubricates 2 membranes, prevents friction during contractions and relaxations

What are the base and apex of the heart?

1. Apex - more pointed, caudal end (shifted to left and sits more ventrally)

2. Base - rounded cranial end of heart (shifted to right and faces more dorsally)

What are the 3 layers of the wall of the heart?

1. Epicardium (outermost)

2. Myocardium (middle and thickest layer)

3. Endocardium (thin membrane that lies on internal surface of myocardium)

What are the 4 chambers of the heart?

1. Two atria - receive blood into heart

2. Two ventricles - pump blood out of heart

What are some facts on the atria of the heart?

1. Left and right atrium separated by interatrial septum

2. Receive blood from veins that carry blood to heart

3. Identified by auricles (blind pouches that come off main part of atria)

What are some facts of the ventricles of the heart?

1. Separated by interventricular septum

2. Visible area of interventricular septum on outside of heart = interventricular groove (contains vessels and fat)

3. Right ventricle pumps blood to pulmonary circulation through pulmonary artery

4. Left ventricle pumps blood through aorta

5. Interventricular septum together = atrioventricular septum

What 2 parts of the heart prevent backflow?

1. Valves - close at specific times to prevent backflow of blood into chamber it came from

2. Chordae tendineae - prevent valves from opening backward (located in wall of both sides of ventricles)

(T/F) Blood flows in 1 direction for the heart to work properly

True

What are the 4 valves of the heart that control blood flow through the heart?

Atrioventricular valves (AV valves)

• Located between atria and ventricles

Tricuspid valve

• Right AV valve w/ 3 flaps/cusps

• Opens when pressure from amount of blood in right atrium forces it open

Bicuspid valve (mitral valve)

• Left AV valve w/ 2 cusps

Semilunar valves

• 2 valves that control blood flow out of ventricles & into arteries

• Right = pulmonary valve; Left = aortic valve

What is the skeleton of the heart and what are its 4 primary functions?

• Located between atria and ventricles - 4 dense fibrous connective tissue rings

1. Separates atria and ventricles

2. Anchors heart valves

3. Point of attachment for myocardium

4. Electrical insulation between atria and ventricles

What armies/veins supply blood to the heart?

• Coronary arteries branch off aorta

• Coronary veins join together near right atrium to form coronary sinus

• Coronary sinus drains into right atrium

What is the vena cava?

Large vein that brings deoxygenated blood from systemic circulation to heart

What are the two “loops” of the figure 8 of blood flow through the heart?

1. One loop represents pulmonary circulation

2. Other loop represents systemic circulation

3. Heart sits in middle pumping blood through loops

What is the cardiac cycle?

• Cycle of atrial and ventricular contraction & relaxation

• Produces 1 heartbeat

• Systole = myocardium contracting

• Diastole = myocardium relaxing

What are the structures of the cardiac conduction system?

1. SA node

2. Atrioventricular node

3. Bundle of His

4. Purkinje fiber system

What creates the “lub” and “dub” sounds of the heart?

Lub

• Atrial systole - tricuspid & mitral valves snap shut

Dub

• Ventricular systole - pulmonary & aortic valves shape shut

What is cardiac output and how is it determined? What is the equation?

• (CO) Volume of blood that is ejected out of left ventricle over a unit of time, usually 1 min

• Determined by: Stroke volume (SV) - systolic discharge, and HR

• Calculation: CO = SV X HR

What is stroke volume and what 2 factors determine it?

• Represents strength of heartbeat

1. Preload - volume of blood received from atrium

2. Afterload - physical resistance by artery the ventricle is ejecting blood into

• Can also be affected by length of cardiac muscle cells

What sets rate of HR for each species internally? What affects external control?

Rate of spontaneous SA node depolarization

• External control comes through automatic nervous system

What are the 2 types of arteries and what are the 2 major arteries?

Types:

1. Elastic

2. Muscular

Major arteries:

1. Aorta

2. Pulmonary artery

What is the function of arteries?

• Carry blood away from heart

• Pulmonary circulation carries deoxygenated blood

• Systemic circulation carries oxygenated blood

What are some characteristics of capillaries?

• Microscopic blood vessels from branching arterials

• Occur in groups called capillary beds/networks

• Walls are 1 endothelial cell thick - exchange of gases & nutrients occurs at this level

What are some characteristics of veins? What are the 2 major veins?

• Carry blood toward the heart (oxygenated blood from lungs; deoxygenated blood and waste materials throughout body)

• Capillaries join together to form venules, and venules into veins

• One-way valves

• All systemic veins drain into vena cava

• Major veins - Vena cava, pulmonary vein

What structures allow for the bypassing of blood from the lungs in a fetus?

1. Foramen ovale

2. Ductus arteriosus

What is the definition of a pulse?

Rate of alternating stretching and recoiling of elastic fibers in an artery as blood passes through with each heartbeat (left ventricle doesn’t eject blood in a continuous flow)

• Most often felt on superficial arteries

What is the definition of blood pressure?

Measure of amount of pressure flowing blood exerts on arterial walls

What are systolic, diastolic, and MAP BP?

1. Systolic = highest number (contraction)

2. Diastolic = lowest number (relaxation)

3. MAP (mean arterial pressure) = average pressure during 1 cardiac cycle

What are 2 methods to determining BP?

1. Oscillometric method - cuff measure magnitude and frequency of pulsations

2. Copper ultrasound - transducer attached to sphygmomanometer

What is an electrocardiography? What are the components of 1 cardiac cycle?

• Based on electrical activity of heart; detects electrical impulses on surface of animal’s body; produces electrocardiogram (ECG/EKG)

• Components = P wave, QRS complex, and T wave

What are some other venipuncture sites (2)?

1. Superficial caudal epigastric vein (milk vein) - lactating dairy cattle

2. Coccygeal vein - ruminants and rodents

What makes up the circulatory system?

Heart, blood, and lymphatics

• Provides oxygen for nutrition and metabolic requirements

What are the 2 divisions of the circulatory system?

1. Blood vascular system w/ heart

2. Lymphatics - lymph vessels, lymph nodes, and lymph organs

KNOW THE PATHWAY OF BLOOD THROUGH THE HEART

Artery vs. Capillary vs. Vein

1. Artery - vessel carrying blood away from the heart; sustains blood under high pressure (carries oxygenated blood except for pulmonary artery)

2. Capillary - microscopic vessels; vessels are permeable to allow for exchange of gases and nutrients

3. Veins - carries blood back to the heart; thin wall, carries greater volume than arteries

What are the general duties of RBC’s, WBC’s, and platelets?

1. RBC’s - carry oxygen

2. WBC’s - neutrophils, lymphocytes, monocytes, eosinophils, basophils; fight disease

3. Platelets - part of clotting mechanism

Serum vs. plasma

1. Serum - blood liquid prior to cellular/platelet clot (clotting agents)

2. Plasma - blood liquid after cellular/platelet clot

Where are most cells produced? Where are they stored?

1. Stored in bone marrow

2. Stored in the spleen

What are bone marrow aspirates used for?

Examine various blood cell development processes (anemic cases); large animal = performed in sternum; small animal = performed in wing of ilium

Hematocrit vs. PCV

1. Hematocrit - centrifugation of blood capillary tube and estimate of total RBC volume compared to total blood volume (estimation of RBC count and hydration status)

2. PCV - venous hematocrit

Endothelium vs. epithelium

1. Endothelium - layer of epithelial cells that lines cavities of heart and blood and lymph vessels

2. Epithelium - covering of internal and external surfaces of body, lining of vessels and other small cavities

Pericardium, Apex, Base, Auricles

1. Pericardium - serous covering over heart (pericardial cavity provides lubrication)

2. Apex - point/tip of heart

3. Base - broad top of heart which receives veins/arteries

4. Auricles - flap/ear like structure of atrium

Coronary groove vs. coronary vessels

1. Groove - depression encircling heart; differentiates between atria and ventricles; contains coronary vessels that feed heart muscle

2. Vessels - coronary artery = vessels that encircle heart and provide nutrients to cardiac muscle

(T/F) Cow has 2 bones w/in the heart

True; os cordae

What are the 4 layers of the heart?

1. Pericardium - bag around heart

2. Endocardium - thin inner layer of heart

3. Myocardium - thick muscle layer of heart

4. Epicardium - thin outer layer of heart

What is bacterial endocarditis?

Common in cows, bacterial disease especially affecting the valves

What is the function of the right atrium of the heart?

• Receives deoxygenated blood from body

• Cranial and caudal vena cava vessels empty into right atrium

• Pectinate muscles - resemble teeth of comb

• Interatrial septum

• Fossa ovale = once was foramen ovale in fetus

What are some characteristics of the right ventricle?

• Receives deoxygenated blood from right atrium

• Pumps blood into pulmonary circulation to be oxygenated

• Pulmonary artery + pulmonary valve

• This muscle is thinner due to not having to pump blood into lungs like the left ventricle

• Tricuspid valve (right atrioventricular valve)

What are some characteristics of the left atrium?

• Receives oxygenated blood from the lungs via the pulmonary vein

What are some characteristics of the left ventricle?

• Receives oxygenated blood from the left atrium

• Sends blood out to the body via the aorta and directly to the heart via the coronary artery

• Aortic valve = semilunar valve

• Left atrioventricular valve = mitral valve/bicuspid valve

Pulmonic vs. systemic circulation

1. Blood that goes to the lungs/passes through the right side of heart

2. Blood that goes to the body/passes through the left side of the heart

What is the function of a valve?

Prevent back flow of blood

What are the 4 main valves and their reason for naming?

1. Right AV (tricuspid) valve = 2-3 leaves/cups forming valve

2. Left AV (bicuspid/mitral) valve = 2 leaves forming valve

3. Aortic (semilunar) valve

4. Pulmonic (semilunar) valve

What is stenosis? Palpation of pulse?

1. Stenosis - narrowing of lumen

2. Palpation - estimate of HR in BPM

Direct vs. indirect BP readings

1. Direct - arterial catheterization w/ manometer gauge, usually of transverse facial artery, facial artery, or great metatarsal artery

2. Indirect - BP cuff readings usually placed around coccygeal artery or great metatarsal artery

What is the necessary MAP for a horse under anesthesia?

MAP of greater than 70mmHg or internal organ perfusion is diminished

What is the normal BP for a human?

130/70

SA node vs. AV node

1. SA node - sinoatrial; in endocardium of right atrial wall ventral to cranial vena cava

2. AV node - atrioventricular; in interatrial septum; gives rise to atrioventricular bundle

What is the atrioventricular bundle?

Mass of modified muscle cells in the atria-ventricular septum; divides into branches called Purkinje Fibers

What is the PQRST wave?

• P = associated w/ depolarization of atria; after depolarization, atrial contraction occurs

• QRS = represents both positive and negative deflections associated w/ ventricular depolarization; ventricular contraction

• T = last wave for each heart beat; represents ventricular repolarization

What is a heart block? What are the 3 degrees?

• Timing of atrial and ventricular contractions are off beat/missing

1. First - conduction time is prolonged but all atrial beats are followed by ventricular beats

2. Second - some, but not all atrial beats are conducted; P wave not followed by a QRS/T wave

3. Third - no impulses are conducted by juctional tissues

What is atrial fibrillation?

Atrium is excessively contracting out of time w/ ventricular contractions

What is sinus arrhythmia?

Physiologic cyclic variation in HR related to vagal impulses to SA node (in animals often associated w/ respiratory/breath patterns altering heart beat)

What are the 3 shunts w/in a fetus?

1. Ductus venosus - connects umbilical vein to caudal vena cava of fetus

2. Foramen ovale - hole in atrial wall that allows blood from right atrium to be shunted/passed directly into left atrium therefore by-passing lungs

3. Ductus arteriosus - connects blood that does reach the immature fetal lungs directly to aorta of fetus

As an adult, what do the 3 shunts present as a fetus become?

1. Ductus venosus - becomes part of portal circulation of liver

2. Ductus arteriosus - becomes ligamentum arteriosum

3. Foramen ovale - closes and becomes depression called fossa ovale

Phlebitis vs. thrombosis vs. ischemia vs. occlusion

1. Phlebitis - infection of vein due to bacteria of a vessel

2. Thrombosis - narrowing of vessel lumen due to inflammation/infection due to bacteria

3. Ischemia - lack of blood flow to region of tissue resulting in death of tissue

4. Occlusion - complete closure of lumen

Where do the carotid arteries go to?

Goes to face, neck, head, and brain

What does the internal carotid artery form?

Joins w/ other arteries to form a circle. Under brain = arterial circle/circle of Willis (forms “blood-brain-barrier”)

What 2 external carotid arteries are used in surgery for equine?

1. Transverse facial and palpebral - catheterized for direct BP in equine undergoing surgery

2. Facial

What are the 2 arteries that go to a horse's hoof?

1. Palmer

2. Digital

Where does the bronchioesophageal artery supply?

Supplies nutrition to the lungs

What are the 5 abdominal arteries?

1. Phrenic - supplies diaphragm

2. Celiac - supplies stomach, part of duodenum, liver, and spleen

3. Gastric

4. Hepatic

5. Splenic - ruminal

What is the cranial mesenteric?

Supplies most of small intestines and cranial aspect of large intestines

What artery supplies the pelvic limb?

External iliac

What artery forms the round ligaments of the bladder?

Umbilical

What is saddle thrombi?

Blood clot in terminal aorta of cats, often blocks external iliac artery causing lameness, paralysis, and limb tissue loss

What are venous valves?

Holding off a vein will dilate the vessel and allow for blood to be withdrawn w/out pressure of blood driving through the hole that was created by the needle; blood will drip w/out a pulsing stream

What are the 7 major veins to know?

1. External jugular - returns blood from head

2. Cephalon - wraps medically around front leg

What is the definition of a capillary?

Minute vessel that connects arterioles to venules, forming a network in nearly all parts of the body; walls act as semipermeable membranes for interchange of various substances

What are the functions of the lymphatic system?

• System returns protein-rich fluid w/in tissues back to the blood circulation

• Part of circulatory system, part of immune system, moves fats from digestive tract into circulatory system

What is the thoracic duct?

Drains entire body except for right chest/limb regions, empties into aortic hiatus

What are lymph nodes? What are the 2 main components of lymph nodes?

• Tissue that course along lymphatic vessel pathway; fluid entering nodes enters via afferent vessels, fluid leaving exits via efferent vessels

1. Primitive cells - cells that will differentiate into immune cells

2. Lymphocenters - groups of lymph nodes that drain regions of the body

What are some characteristics of the spleen?

• Largest lymphoid organ in the body

• Left side of body; attached to stomach

• Produces RBC in fetus and stores RBC in adults

What are Peyer’s patches?

W/in wall of ileum of GI tract; lymphatic tissue

What are 3 important lymph nodes in the head and neck?

1. Parotid - drains head, orbit, parotid gland

2. Mandibular - drains head

3. Retropharyngeal - drains head and neck; not palpable in healthy animal

What is 1 important lymph node in the thoracic region?

• Cervical - drains front shoulder, neck, and dorsal thoracic regions

What is 1 important lymph node in the abdominal region?

• Cranial mesenteric

What is the importance of the thymus?

• Lymphoid organ consisting of 2 pyramidal lobes situated in anterior mediastinum

• Production of T-lymphocytes; max at puberty

What are the 2 steps of respiration?

1. External respiration (occurs in lungs) - exchange of CO2 and O2 between air inhaled and blood in pulmonary capillaries

2. Internal respiration (occurs all over body) - exchange of oxygen and CO2 between blood in capillaries all over body and cells and tissues of body

What are the secondary functions of the respiratory system?

1. Voice production

2. Body temp regulation

3. Acid-base balance regulation

4. Sense of smell

What are the 2 steps of respiration?

1. External - exchange of oxygen and CO2 between air inhaled and blood in pulmonary capillaries

2. Internal - exchange of oxygen and CO2 between blood in capillaries all over body and cells and tissues of body

List 4 secondary functions of the respiratory system

1. Voice production

2. Body temp regulation - inhaled air is warmed to prevent hypothermia; panting increases evaporation of fluids to cool circulating blood

3. Sense of smell

4. Acid-base balance regulation - respiratory influences amount of CO2 in blood of rate of breathing; more CO2 = lower blood pH

What function do the nose and nasal passages have among the respiratory system?

• External opening of respiratory tube = nostrils = nares

• Nasal passages lie between nares and pharynx

• Midline = nasal septum

• Turbinates divide each nasal passage into 3 main passageways (ventral, middle, and dorsal nasal meatus)

What is the main function of the nasal passages?

• Condition inhaled air

• Warming

• Humidifying

• Filtering

Nasopharynx vs. oropharynx

• Divided at rostral end by soft palate

• Nasopharynx = respiratory

• Oropharynx =digestive