Cardiac Cycle and Heart Sounds

• Cardiac Cycle refers to one complete heartbeat.
• The heart is actually 2 pumps situated side by side, so a complete cycle consists of contractions of both atria and both ventricles.
• The average resting heart rate is approximately 75 beats per minute
• Resting heart rate will vary with degree of physical conditioning as well as with disease states
• The familiar “lub-dub” associated with the function of the heart are known as heart sounds.
• The heart sounds are made by the heart valves snapping closed under contractile pressure.

• The “lub” is caused by the closure of the AV valves
• The “dub” is caused by the closure of the semi-lunar valve.
• Cardiac output (CO) is the amount of blood pumped out of each side of the heart ( meaning the ventricles ) in one minute
• The value of CO is calculated as the product of the Heart Rate ( HR) multiplied by the Stroke Volume (SV)
• SV generally increases as the force of the ventricular contractions increases.
• CO = HR  x SV
• CO = 75 beats per min x 70mls per beat
• CO = 5250 ml/min
• Generally speaking, blood starting in the heart should complete a circuit of the body and arrive back in the heart in one minute.
• According to Starling’s Law of the heart, stroke volume is influenced by the amount of stretching force applied to the muscle cells of the heart.
• The more the cells are stretched, the great the contraction will be

Starling’s Law of the Heart

• A healthy, efficient heart only pumps about 60% of the volume of blood in the ventricles.
• Venous return is critical to the amount of stretching the heart undergoes.
• If one side of the heart begins to pump more blood than the other, the increase in venous return to the opposite ventricle will force it to pump a larger volume of blood.
• This helps prevent back ups and increased pressures in the system.
• Anything that increases the volume or speed of venous return will also increase the SV and CO.
• The squeezing actions of skeletal muscles on veins also plays a major role in increasing venous return.

Regulation of Heart Rate

• Coronary contraction does not depend on stimulus from the nervous system, because the heart has it’s own intrinsic pacemakers ( SA and AV nodes)
• HOWEVER—heart rate can be temporarily influenced by stimulus from the autonomic nerves.

• Sympathetic nerves can act to increase or decrease the heart by stimulating the SA or AV nodes.
• Parasympathetic nerves act to decrease the heart rate
• Being excited or startled can cause a rapid increase in heart rate.
• Heart rate can also be influenced by hormones
• Epinephrine and Thyroxine mimic the effects of the sympathetic nerves.
• Ion concentrations also has a rofound influence on the heart.
• Decreased Ca+ will depress the heart rate
• Excessive Ca+ will cause prolonged contractions, and possibly stop the heart from beating.

CHF and Blood Vessels

• When the pumping efficiency of the heart is depressed so that circulation is inadequate to meet tissues needs, congestive heart failure (CHF) results.
• CHF is usually a progressive condition, and in most cases reflects diminished coronary circulation by coronary atherosclerosis
• Each side of the heart can fail independently
• If the left side fails, pulmonary congestion will occur.
• The right side continues to pump blood, but the left side is unable to push oxygenated blood into systemic circulation
• The blood vessels of the lungs become swollen with blood, and the increased pressure forces fluids to leak from circulation and into the lung tissue, resulting in pulmonary edema.
• Suffocation will result if this condition is untreated.
• If the right heart fails, blood is not moved out of the systemic circulation, and peripheral congestion will occur.
• This results in edema in distal parts of the body, such as the feet, ankles and hands.
• Failure of one side of the heart places increased strain on the opposite side of the heart—eventually leading to whole heart failure

Blood Vessels

• Blood circulates through the body within the vasculature.
• In decreasing size order, vessels carrying blood away from the heart are, arteries, arterioles, capillary beds.
• In increasing size order, vessels carrying blood back towards the heart from the capillary beds are, venules, and veins

• The walls of most blood vessels consist of three layers called tunics.
• The innermost layer is called the tunica intima.
• Tunica intima consists of a thin layer of closely fitted endothelial cells.
• It is very smooth, to allow for smooth flow of blood
• The tunica media is the middle layer of tissue, and is primarily smooth muscle tissue and elastic connective tissue.
• This smooth muscle is controlled by the sympathetic nervous system, which changes the diameter of the blood vessels
• The tunica externa is the outer-most layer, and is mostly fibrous connective tissue that supports and protects the vessel.
• The walls of arteries are usually thicker than those  of the veins.
• Veins are subject to less pressure than ateries, but move blood against gravity.
• Veins contain one way valves to prevent backflow of blood

Hormone Functions

•          ACTH (adrenocorticotropic hormone)

•         Regulates the activity of the cortex of the adrenal gland

•          TSH (thyroid stimulating hormone)

•          Stimulates production and release of thyroid hormone

•          GH (growth hormone)

•          Stimulates growth of bones, cartilage, muscle

•          Timing and amount released determines body size

•          PRL (prolactin)

•          Stimulates breast development

•          Promotes and maintains lactation after childbirth

•          FSH (follicle stimulating hormone)

•          Causes formation of ovarian follicles and stimulates them to produce estrogen

•          Stimulates sperm development in men

•          LH (luteinizing hormone)

•          Initiates ovulation, maintains corpus luteum

•          Regulates testosterone production in males

•          ADH (antidiuretic hormone)

•          Reduces urine output by increasing water reabsorption in the kidney

•          Plays small role in blood pressure regulation

•          Oxytocin

•          Causes uterine contractions in labor

•          Causes milk let down in lactating mothers

•          Thyroid Hormone

•          Regulates metabolic rate of the entire body

•          Important in development of the nervous system

•          Calcitonin

•          Decreases bone reabsorption, lowering serum calcium levels

•          PTH (parathyroid hormone)

•          Increases serum calcium

•          Decreases serum phosphorus

•          Insulin

•          Released in response to high blood sugar

•          Increases cellular absorption of glucose

•          Increases rate of lipogenesis and formation of glycogen in the liver

•          Glucagon

•          Released in response to low blood sugar

•          Increases rate of gluconeogenesis (formation of sugar from fat and protein)

•          Increases lipolysis and glycogenolysis

•          Epinephrine & Norepinephrine

•          Fight or flight response

•          Increase heart rate, increase skeletal muscle blood flow, decrease skin blood flow

•          Glucocorticoids (Cortisone)

•          Released in response to stress

•          Increases formation of glucose from protein and fat breakdown

•          Decreases inflammation

•          Aldosterone

•          Increases blood volume by causing kidneys to retain sodium (where sodium    goes water goes too) in exchange for potassium

•          Increased blood volume will increase blood pressure

•          Androgens

•          Initiates pubertal changes

•          Precursors to estrogen in postmenopausal women

•          Melatonin

•          Involved in circadian rhythms

•          Day ¯ melatonin, Night ­ melatonin

•          Produces sleepiness

•          Erythropoietin

•          Stimulates RBC production

•          Calcitriol

•          Stimulates calcium and phosphate absorption

•          Stimulates calcium release from bone

•          Inhibits PTH secretion

Diabetes

•          Type 1: Insulin Dependent Diabetes

•          AKA: juvenile diabetes

•          Caused by a lack of insulin

•          Autoimmune disorder

•          Immune system destroys beta cells in the pancreas

•          Type 2: Non-Insulin Dependent

•          Caused by an insensitivity of cells to insulin.

•          Diabetes mellitus marked by hyperglycemia

•          ­ urine production (polyuria)

•          ­ thirst (polydipsia)

•          ­ eating (polyphagia)

Diagnosing Diabetes Mellitus

•          Normal blood glucose levels: 70-100 mg/dl

•          Diabetes mellitus:

•          A fasting glucose level above 140 mg/dl on two separate occasions, or

•          A blood sugar over 200 mg/dl 2 hours after oral glucose tolerance test with    75gm of glucose

•          Impaired Glucose Tolerance (Pre-Diabetes)

•          A fasting glucose level between 100-126 mg/dl on two separate occasions,      or

•          A blood sugar between 140-200 mg/dl 2 hours after oral glucose tolerance      test with 75gm of glucose

Anatomy

1. Gross anatomy: the study of body structures visible to the naked eye (without a microscope)
2. Microscopic anatomy:

• Cytology: Analysis of the internal structures of individual cell
• Histology:  examination of tissues (groups of specialized cells that work together to perform a specific function.

Anatomical Position

1. Anytime you describe structures relative to one another, you must assume this standard position:

• Body erect
• Feet slightly apart        
• Palms facing forward     
• Thumbs point away from body

Anterior Landmarks

PosteriorLandmarks

Anatomical Locations

•         Abdominal: abdominal region

•         Acromial:  the point of the shoulder

•         Antebrachial:  forearm

•         Antecubital: anterior surface of the elbow

•         Axillary: armpit

•         Brachial: upper arm

•         Buccal: cheek of the face

•         Calcaneal:  heel of the foot

•         Carpal:  wrist

•         Cephalic:  head

Anatomical Locations

•         Cervical:  neck

•         Deltoid:  round part of the shoulder

•         Digital:  fingers and toes

•         Dorsum:  back

•         Femoral:  thigh

•         Frontal:  forehead

•         Gluteal:  buttocks

•         Hallux:  big toe

•         Inguinal:  groin

•         Lumbar: lower back

•         Mammary:  breast

Body Orientation and Direction

•         These are relative positions

•         Proximal/distal

•         Used to describe locations on the arms and legs

•         GI tract

•         Medial/lateral

•         Medial is closer to the midline

•         Farther away from the midline

Body Orientation and Direction

•         Dorsal: Back

•         Ventral: Front

•         Superior or Cephalad is toward the head

•         Inferior or Caudal is toward the feet

•         Anterior: most forward

•         Posterior: toward the backside

Planes of the Body

Dorsal Body Cavity

•         Dorsal cavity protects the nervous system

•         Contains Brain and Spinal Cord

Cavities

Serous Membranes

•         Serous Membranes have two layers

1.      Parietal serosa lines internal body walls

2.      Visceral serosa covers the internal organs

3.      Serous fluid separates the serosae

Serous

Serous Membranes of the Heart

Quadrants

Abdominopelvic Regions

Blood Vessels & Circulation

Artery and Vein Histology

•          Walls have 3 layers:

•          Tunica intima

•          Tunica media

•          Tunica externa

Tunica Intima

•          Is the innermost layer near the lumen

•          Includes:

•          The endothelial lining

•          Connective tissue layer

•          Internal Elastic Membrane:  In arteries, is a thick layer of elastic fibers in the     outer margin of the tunica intima

Tunica Media

•          Is the middle layer

•          Contains concentric sheets of smooth muscle in loose connective tissue

•          Binds to inner and outer layers

Tunica Externa (aka: Tunica Adventitia)

•          Is outer layer

•          Contains connective tissue sheath

•          Anchors vessel to adjacent tissues

•          In arteries:

•          Contain collagen

•          Elastic fibers

•          In veins:

•          Contain elastic fibers

•          Smooth muscle cells

Arteries Vs. Veins

•          Arteries and veins run side-by-side

•          Arteries have thicker walls and higher blood pressure

•          Collapsed artery has small, round lumen

•          Vein has a large, flat lumen

Arteries

•          Carry blood away from the heart.

•          Pulmonary arteries: The pulmonary trunk and its branches;  leave the right ventricle of the heart and contain deoxygenated blood.

•          Systemic arteries: The aorta and its branches;  leave the left ventricle of the heart and contain oxygenated blood.

Elastic Arteries

•          Also called conducting arteries, these are the largest arteries

•          Tunica media has many elastic fibers and few muscle cells

•          Elasticity evens out pulse force

•          Examples:

•          Pulmonary trunk

•          Aorta

•          Common carotid arteries

•          Subclavian arteries

•          Common iliac arteries 

Muscular Arteries

•          Also called distribution arteries, are medium-sized (most arteries)

•          Tunica media has many muscle cells

•          Examples:

•          External carotid arteries

•          Brachial arteries

•          Femoral arteries

Arterioles

•          The smallest branches of arteries

•          Feed into capillaries

•          Have little or no tunica externa

•          Have thin or incomplete tunica media   

Capillaries

•          The smallest vessels

•          Structure: Simple squamous epithelium tube

•          Lumen side has a thin basal lamina

•          No tunica media, No tunica externa

•          Location of exchange between blood and interstitial fluid.

•          Gasses and chemicals diffuse across their walls

•          Types:

•          Continuous

•          Fenestrated

•          Sinusoids

Continuous Capillaries

•          Have complete endothelial lining (most common type of capillary)

•          Permit diffusion of:

•          Water

•          Small solutes

•          Lipid-soluble materials

•          Prevent diffusion of:

•          Blood cells

•          Plasma proteins

Fenestrated Capillaries

•          Have pores in endothelial lining

•          Permit rapid exchange of water and larger solutes between plasma and interstitial fluid

•          Are found in:

•          Choroid plexus

•          Endocrine organs

•          Kidneys

•          Intestinal tract

Sinusoids

•          Modified, extremely leaky, fenestrated capillaries

•          Found in locales where large stuff needs to exit/enter the bloodstream.

•          Liver

•          Spleen

•          Bone marrow

•          Endocrine organs

Veins

•          Carry blood to the heart

•          Are larger in diameter than arteries

•          Have thinner walls

•          Contain valves

•          Folds of tunica intima that prevent blood from flowing backward

•          Venules: The smallest veins that carry blood away from the capillaries

•          Medium-sized veins:

•          Thin tunica media and few smooth muscle cells

•          Tunica externa with longitudinal bundles of elastic fibers

•          Large veins:

•          Have all 3 tunica layers

•          Thick tunica externa

•          Thin tunica media

•          Example: Inferior and Superior vena cava