KNPE 125 UNIT 3

Immunity

Immunity

the immune system’s capacity to protect individuals from disease by recognizing and eliminating potentially pathogenic agents

Immune response and the 2 types

complex series of physiological events that culminates in the destruction and elimination of these substances.

1. Non-Specific (innate)

   1. `First defenses against pathogens regardless of the type of pathogen

2. Specific (adaptive)

   1. Stronger defense against a specific pathogen(s) that takes longer to develop

inappropriate immune response

allergies, autoimmune diseases, rheumatoid arthritis, diabetes mellitus, multiple sclerosis, etc

Pathogen and the 4 types

any organism that has potential to cause disease

includes virus (smallest), bacterium (ex; salmonella or strep), fungi (ex; yeast infection, athletes foot) , parasites (ex; worm, ticks, flee, lice)

Physical and chemical barriers

First line of defense against pathogens. The epithelium has two components:

1. Skin: Epidermis (outer) layer and dermis (inner) layer

2. Mucous Membranes:

   1. Continuous barrier with the skin

   2. Viscous mucus (goblet cells): tries to trap pathogens

   3. Acid (lysosomes): tightly regulates pH that allows acids to degrade pathogens

Leukocytes

white blood cells located in the blood stream and in other tissues. They are able to squeeze through pores in capillaries and migrate through tissues. There are 5 types:

The granulocytes: Eosinophils, Neutrophils, Basophils,

The agranulocytes: Monocytes, Lymphocytes

Haematopoiesis

Creation of new blood cells. Process begins with a multi-potential stem cell in the bone marrow of adults (or liver in fetus). Multi-potential stem cell can give rise to any and all blood cells; initial division into either

1. Myeloid cell creates a common myeloid progenitor (CMP) via Myelopoiesis

2. Lymphoid cell creates a common lymphoid progenitor (CLP) via Lymphopoiesis

Phagocytes

A type of leukocyte that engulfs foreign particles and microorganisms, thereby removing them from blood and tissue. Referred to as the pacman cell.

• Secrete cytokines (cell signaling molecules)

• Circulate the blood for 7-10 hours

• Migrate to tissues for a few days

• Increase in numbers during infections

Includes Neutrophils, Monocytes, Macrophages, Dendritic Cells, Eosinophils

Lymphocytes

type of leukocyte that provides the immune system with diversity, specificity, memory, and the ability to distinguish between self and non-self

Lymphocytes account for 20-40% of leukocytes. Leukocytes account for 99% of interstitial fluid cells.

Includes B-Lymphocytes (B-Cells), T-Lymphocytes (T-Cells), Null Cells (Natural Killer Cells)

Lymphatic system

Central lymphoid tissue (primary): Site of lymphocyte production and maturation

• In adults: bone marrow, thymus

• In fetus: liver

Peripheral lymphoid tissues (secondary): Site of initiation of the adaptive immune response

• Primary: lymph nodes, spleen

• Secondary: Mucosae or mucosal-associated lymphoid tissues (MALTs)

  • Peyer's patch in the small intestine, tonsils, adenoids in throat and nose, appendix, lymph nodes

Roles of Peripheral Lymphoid Tissue

1. Filters bodily fluids

2. Removes potentially harmful material (pathogens from blood)

3. Stores leukocytes

Innate (Non-Specific) Immunity

Second line of defense (after physical and chemical barriers), recognize a pathogen but not specifically

1. Physical Barriers

2. Inflammation

3. Interferons

4. NK Cells

5. The complement system

Purpose to remove harmful agents, clean up the infection and help repair injured tissue

What is inflammation?

A non-specific rapid response via accumulation of proteins, fluids, and phagocytic cells in an area of tissues that has been injured or invaded by microorganisms

Induced by chemical mediators from invading pathogens, release by damaged cells, release by leukocytes, movement from blood to the infected tissue

Hallmark signs of inflammation: Heat, Pain, Redness and Swelling

Steps of inflammation

1. Nearby macrophages engulf the debris and foreign matter

2. Nearby capillaries dilate and become more permeable to proteins and fluid

3. Foreign matter is contained

4. Additional Leukocytes migrate into the region

5. Recruited leukocytes continue to help clear the infection; phagocytosis

Step 1 of inflammation: Macrophages engulf foreign material

Macrophages are phagocytes that perform phagocytosis aka engulf foreign material.

They have receptors that detect pathogens (PRRs). The receptors grab a hold of bacteria & begin phagocytosis

They then release cytokines; Small signalling protein that signal other immune cells, which causes inflammation

Steps of phagocytosis

1. Attachment: Bind to rough/irregular cell shapes using PRR receptors (not healthy cells)

2. Internalization: Fully surround bacteria and bring inside cell. Takes < .01 seconds!

   1. Phagosome: pathogen/foreign material inside a phagocyte

3. Degradation: Enzymes (lysosomes) breakdown pathogen

   1. Phagosome + lysosome = secondary lysosome

4. Exocytosis: Eliminates harmless waste

Step 2 of inflammation: Capillaries dilate & become more leaky

Local dilation of blood capillaries by histamine increase blood flow, which leads to warm and red skin

• Causes gaps between endothelium cells for increased leakage of blood plasma

• More blood flow and leakage leads to edema (swelling)

  • This causes an increase in pressure on nerves and leads to pain

Step 3 of inflammation: Containment of Foreign Material

Need to reduce the spread of foreign material. Clotting factors are released from the blood and form a clot around bacteria

Heparin keeps area from clotting for a short period of time allowing entry of leukocytes

Step 4 of inflammation: Leukocyte Migration and Proliferation

Leukocytes (reinforcements) migrate to injury site. Other phagocytes that join the clean up effort

Bone marrow increases production of leukocytes because more are leaving to the site of injury

Adaptive (Specific) Immunity

Specificity, diversity, memory, self-tolerance. Specialized response initiated by an infection. Takes days to weeks after exposure to develop. Able to recognize specific pathogens and able to remember previous pathogens.

1. Humoral Immunity

2. Cell-Mediated Immunity

How do B and T cells identify pathogens?

Detect molecules called antigens: Unique proteins on foreign/damaged cells, like a fingerprint.

• Antigens bind to antigen binding sites on lymphocytes that have specific shapes only!

What happens when antigens bind to T lymphocytes?

CD4 T cells help (ENHANCE activity) other cells by secreting Cytokines (helper T cells)

CD8 T cells kill the bad cell; a license to kill (cytotoxic T cells)

What happens when antigens bind to B lymphocytes?

B cells can develop into …

1. plasma cells known as antibody-synthesizing factory and release antibodies into circulation

2. Memory cells where antibodies bind to antigens, marking them for destruction

Antibodies + 3 roles

Released by B lymphocytes into circulation. Antibodies bind to antigens in circulation, marking them for destruction. 3 roles:

1. Neutralize/block antigen (pathogen) activity

2. Clump pathogens into a big group (easier to clean up)

3. Enhance the activity of macrophages and other immune cells

Memory B and T cells

When activated by an antigen, B and T lymphocytes can create ‘clones’ called Memory B or T cells. If that same pathogen comes back, the body will be ready to quickly fight it off

Primary vs secondary response

Primary response: first exposure to antigen

Secondary response: second exposure to the same antigen

• Can take quite a long time to begin to make antibodies after first exposure (10-17 days), and you feel sick

• After second exposure it only takes 2-7 days to fight off sickness

Vaccinations creation

Created by Edward Jenner with the invention of the smallpox vaccine in 1796-1798. He noticed that milkmaids that had been ill with cowpox appeared to be immune to smallpox. Cowpox is a similar, but far less aggressive version of smallpox. He predicted that deliberate inoculation with cowpox would protect people against smallpox.

Vaccination/immunization

Introduction of a safe form of a microorganism or a collection of its components (inoculum) that are not expected to cause disease into the body. Exposure to an antigen causes a slow, weak primary immune response and induces immunological memory.

• Lymphocytes detect antigen and we start building immunity

• When natural exposure occurs after vaccination, there is a fast and strong secondary immune response

Herd immunity

If a large portion of the population is vaccinated (protected), the rate of disease transmission is likely to be significantly lower than not protected

What are allergies

aka hypersensitivity reactions; Exaggerated immune response to environmental antigens called allergens

• Pollen, dust, pet dander, types of food, bees, etc.

• Some responses are more serious than others...

  • Life threatening = anaphylactic shock (widespread degranulation of mast cells causes bp to drop)

  • In low-grade reactions the main issue is usually vasodilation and capillary permeability

How does the immune system cause allergies

Excess production of specific antibodies by B cells, which bind to leukocytes (mast cells), which triggers degranulation

• the release of histamine induces inflammation

• anti-histamines prevent histamine from having the effect it normally has

Autoimmune disorders

An important feature of a healthy immune system is “self-tolerance”; Ability to recognize OWN cells vs. FOREIGN cells

This feature is dysfunctional in autoimmune disorders. Immune cells attack specific cells of the body

Multiple sclerosis

Immune system (T cell lymphocytes) attacks the myelin sheath on nerves of the central nervous system, so nerve Impulses traveling along nerves are interrupted or distorted.

Symptoms:

• Impaired Vision

• Sensory Problems

• Weakness in Limbs

• Loss of Coordination

• Speech Problems

• Short Term Memory Loss

• Fatigue

What is a possible explanation for multiple sclerosis?

Only specialized T cells are allowed in the brain and the blood-brain barrier controls T cell entry. An infection may change blood-brain barrier function and allows non-specialized T cells to enter brain tissue and attack myelin

Evidence: activated cytotoxic T cells are found in the cerebral spinal fluid of people with MS that are not found in healthy adults

Type 1 diabetes

Destruction of insulin-producing beta cells in pancreas leads to a lack of insulin which causes a whole plethora of problems.

People with T1D must regularly take insulin and regularly monitor their blood glucose.

What is a possible explanation for type 1 diabetes?

T cells wrongfully attack beta cells of the pancreas and destruction of beta cells = no more insulin.

Cause is not known but people with a certain type of major histocompatibility complex receptor (MHC) are prone to type 1 diabetes.

Normally, T cells identify antigens using MHCs type of receptor. Every cell in the body has an MHC and they tell T cells if the cell is a “Friend or Foe”. When a cell is infected, the MHC presents the antigen, telling the T cell “foe”. In type 1 diabetes, beta cells display a ‘friend’ MHC, but T cells misread it and break the cell down.

Anatomy of the renal system

• We have two kidneys and two ureters, one bladder, one urethra

• urethera is how we excrete

Anatomy of the kidney

• Outer edge is renal cortex

• Striated section is renal pyramids; part of medulla

• Nephrons are the yellow pieces

• Blue is veins

• Red is arteries

• Nephrons include blood vessels and bowmans capsule which make renal corpuscal

Types of nephrons

• Juxtamedullary nephrons have a longer lop of henle that descend farther

• Cortical nephrons are more common and have a short loop of henle

Juxtaglomerular Apparatus

• Renal corpuscle/juxtaglomerular apparatus has two components; glomerulus and bowman’s capsule

• Blood flows into kidney through arteries

  • Afferent artery delivers blood to Bowmans capsule

• Filtrate; once it moves from the blood into the Bowmans capsule

Blood supply to kidneys

• Renal artery splits into segmental arteries, then interlobular arteries

• Afferent arteriole brings blood to the glomerulus and the efferent arteriole carries blood away from the glomerulus

• Peritubular capillary wrap around tubules

  • Increases surface area when they are wrapped around each other

• Absorption and filtration allows us to stay at homeostasis

• Blood enters through renal artery and comes out through the renal vein

Renal processes

1. Filtration: Removal of H2O, ions and molecules from the blood into the kidney filtrate

2. Tubular Reabsorption: Uptake of H2O, ions and molecules from the kidney filtrate back into the blood

3. Tubular Secretion and continued Reabsorption: Selective removal of substances from the blood into the kidney filtrate and the uptake of H20 from the kidney filtrate into the blood

4. Excretion: Elimination of solute and water from the body in the form of urine

Rate of excretion equation

Rate of Excretion = Filtration + Secretion - Reabsorption

Renal corpuscule

2 Major Components:

1. Glomerulus – blood supply, fed by afferent arteriole

   1. Filters 20% of plasma volume that passes through

   2. Bundled vessels increase surface area

   3. Unfiltered blood leaves via efferent arteriole

2. Bowman’s Capsule – filtrate accepter

• nutrients, vitamins, chemicals, and waste can cross the membrane to filter

  • proteins and cells can not

• High pressure in glomerulus drives contents from the blood to Bowman’s capsule

  • Move from HIGH to LOW pressure

  • Passive process

Tubular Reabsorption

filtered solutes and water moving from the tubules into the plasma. Occurs in the proximal convoluted tubule (mass absorber) following filtration into Bowmans.

• Highly permeable tubule

• Important molecules are reabsorbed back into blood (glucose, vitamins, amino acids, H2O, bicarbonate, K+)

• Not well regulated

• ~70% of sodium and water in filtrate reabsorbe

• Reabsorption occurs via diffusion and active transport

What are the reasons the proximal convoluted tubule has such high reabsorption?

1. Brush Border: Finger like projections increases surface area (increases conductance) in proximal convoluted tubule

2. Lots of Mitochondria: Make ATP for energy for lots of active transport

3. “Leaky” Epithelium: Allows molecules to flow across the membrane (no tight junctions)

Peritubular capillaries

capillary that wraps around the proximal distal tubule and reabsorb H2O and molecules that diffuse out of proximal convoluted tubule

Descending loop of Henle

Only permeable to H2O, so large amounts of H2O leave filtrate when osmotic gradient exists. No Na+, K+, Cl-, transport.

• No transporter in the body for H2O

• H2O moves down it’s osmotic gradient; high [H2O] to low [H2O]

• Gradient created by the movement of solute (Na+, Cl-) from Ascending Loop of Henle into the Vasa Recta

• Amount of solute transported is directly proportional to the amount H2O reabsorption

Ascending Loop of Henle

Impermeable to H2O. Actively pumps Na+, K+, Cl-, (co-transport) out of filtrate

Vasa recta

A capillary wrapping around the loop of henle that reabsorbs H2O, Na+ and Cl-

Active transport of Na+ Cl- from the ascending limb

1. Na+/K+/Cl- co-transporter moves ions out of tubule into epithelial cells

2. K+ diffuses through K+ channel back into tubule

3. Cl- diffuses into interstitial space through Cl- channel

4. Na+ pumped out of epithelial cells via Na +/K + pump

in total, more Na+ moves across epithelial cells than K+ creating an osmotic gradient

Distal convoluted tubule

Substances are secreted into the tubule from the blood via diffusion and active transport

Urea, ammonia, H+, K+, foreign substances (i.e. drugs)

Collecting ducts

as the remaining filtrate passes through the collecting ducts, H2O is reabsorbed

antidiuretic hormone

Collecting ducts reabsorb water only in response to antidiuretic hormone (ADH).

ADH is released by pituitary gland when water needs to be reabsorbed (i.e. sweating, low water intake, low blood pressure, etc.)

ADH release inhibited when water needs to be excreted (i.e. after drinking a big glass of water, high blood pressure)

ADH process

1. ADH stimulates receptor on collecting duct

   1. ADH travels in the blood and moves to the interstitial space when it reaches the collecting duct and stimulates receptors on the outside wall of collecting duct

2. Causes aquaporin-2 to be present on cell wall of inside of collecting duct

3. Aquaporin-2 allows water to diffuse down its osmotic gradient

   1. Increases conductance for flow of water from filtrate into the interstitial space then the peritubular capillaries

Excretion

Filtrate is excreted as urine (urination = micturition)

• Once the filtrate enters the collecting ducts it drains into the renal pelvis

• Renal pelvis to Ureter, then Ureter to Bladder

  • Wave like contraction of smooth muscle surrounding ureter push the urine down the ureter

• Micturition (urine) reflex stimulated when there is fluid buildup in the bladder to create urination

  • there are smooth muscles (detrusor) for involuntary control and skeletal muscles for voluntary control

Primary purposes of the lung

1. Allow oxygen (O2) to diffuse into blood

   1. needed for ATP synthase

2. Allow carbon dioxide (CO2) to diffuse out of blood

   1. buildup of CO2 is toxic

External respiration

1. Pulmonary ventilation

2. Exchange of O2 and CO2 between lungs and blood

3. Transport of O2 and CO2 to the tissues

4. Exchange of O2 and CO2 between blood and tissues

Upper airway and respiratory tract

Begins at mouth and nose, makes its way through system (epiglottis, glottis, trachea, larynx) and ends at alveoli where gas exchange occurs. Two distinct zones:

1. Conducting Zone

2. Respiratory Zone

terminal bronchial

once the broncials becomes less than 1mm in diameter

The conducting zone

Consists of trachea, branches, and bronchioles. Carries (conducts) air from the mouth/nose into the lungs. Trachea branches and bronchioles enter lungs.

Contains ‘dead space’ air where no gas exchange occurs. Until a breath is larger than 150mL in volume, no gas exchange occurs.

The respiratory zone

Active/functional portion of the lung, where gas exchange actually occurs. Bronchioles branch into individual respiratory units. Alveoli are where gas exchange takes place.

Alveoli

functional unit of the respiratory zone. There are ~300 million alveoli in the lungs. Total surface area of ~100 000 cm^2.

Respiratory membrane

Alveoli are open sacs, surrounded by capillaries. Almost 1000 km of capillary are laid over the alveoli. Huge surface area for gas exchange = huge conductance for diffusion of O2 and CO2

• 0.2 μm thick

• ↑↑ conductance for gas exchange

Trachea anatomy

2.5 cm in diameter, 10 cm in length, Total surface area of ~78 cm

Chronic Obstructive Pulmonary Disease

Inflammation of alveoli and a mucous build up causes a permanent destruction of alveolar walls, which severely reduces capacity for gas exchange in alveoli'.

Thoracic cavity

Includes two main components:

Chest Wall: Includes rib cage, sternum, thoracic vertebrae, connective tissue, intercostal muscles. Airtight sealed system which protects the lungs.

Diaphragm: Divides thoracic cavity and abdominal cavity. Primary inspiratory muscle.

Pleura

Intrapleural space maintains negative pressure between the lung and chest wall, which keeps the lung expanded and allows them to stay connected. Each lung is surrounded by a separate pleural sac.

As the chest wall or lung moves, they move together. At rest there is elastic recoil pulling chest wall in one direction and elastic recoil pulling lung in the other direction.

Pneumothorax

Lung collapse. Occurs when the pleural sac is punctured. The negative pressure is filled with air and the connection between lung and chest wall no longer exists, so the lung pulls away from chest wall

Each lung is separate in this case; only one can collapse and the other can be fine because lungs are individually wrapped in their own pleural sac.

Flow of breathing mechanisms

• Phi: Atmospheric Pressure = Patm

  • Remains relatively constant at ~760 mmHg

• Plo: Alveolar Pressure = PA

  • Change in pressure here affects gradient for flow

  • Amount of pressure in alveoli; we can actively change this through respiration

• Resistance = R

  • Depends on airway radius

  • Opposite of conductance

  • Generally very constant

Inspiration vs expiration

Inspiration: lungs expand during inspiration

• PA decreases

• △P drives air into the lungs

• Alveolar volume increase

• Expansion creates a negative pressure: alveolar pressure becomes more negative which increases flow into the lungs

  • We are subtracting a more negative number so flow increases

Expiration: Lungs recoil during expiration

• PA increases

• △P drives air out of the lungs

• Alveolar volume decreases

Passive vs active expiration

• At resting level, there is passive expiration which is simply relaxation of the muscles

• Active expiration is 'forced' intentional expiration

Neural control of ventilation

There is both voluntary and involuntary control of breathing

Feedback Control System: ventilation is adjusted in order to maintain concentrations of blood gases (O2 and CO2)

Feedback Controller (Integrator): respiratory control center in medulla of brain stem. Adjusts firing rate of α-motor neurons of respiratory muscles, which impacts the diaphragm and intercostal muscles.

Which motor nerves are connected to the respiratory center?

1. Phrenic Nerve: diaphragm muscle

2. External IC Nerve: external intercostal muscles

3. Internal IC Nerve: internal IC muscles

• Motor nerve stimulates muscles

• Respiratory muscles are skeletal muscles

Flow of gas exchange

Gas exchange = (Phi x Plo) x K

• More oxygen brought into the lungs = higher drive for diffusion flow

• CO2 moves the opposite direction as O2 (blood to alveolar space)

• Conductance for flow into blood is respiratory membrane (constant; not increasing or decreasing)

• Diffusion of gas is determined by pressure gradients

Gas solubility

• O2 has low solubility in water

• Partial pressure is not necessarily about the number of molecules, it is about the dispersion and solubility

Hemoglobin

Because of the low O2 solubility in the blood, hemoglobin (Hb) is used to transport O2. 98.5% of all oxygen is transported in the blood by hemoglobin.

Hemoglobin has heme (iron containing group) and globin (4 polypeptide groups). Oxygen binds to the heme group.

Because Oxygen is bound to the heme groups, there is a reduced partial pressure of dissolved O2 in the blood, which maintains gradient for diffusion of new oxygen.

No O2 bound to hemoglobin = Deoxyhemoglobin

O2 Bound to hemoglobin = Oxyhemoglobin

Factors affecting diffusive conductance

1. Thickness of barrier: single cell separates air and blood

2. Surface area: 1000km of capillaries laid of 100,000 cm2 of alveoli. Larger surface area = more diffusion.

3. Ability of gas to diffuse: O2 and CO2 = fat soluble, therefore easily diffuse across a membrane

atmospheric partial pressures of gases

PO2 = ~21% x 760 mmHg (sea level atm pressure)

• 160 mmHg

PCO2 = ~0.03% x 760 mmHg

• = 0.23 mmHg

PN2 = ~79% x 760 mmHg

• = 600 mmHg

Partial pressures of different gases in different body parts

• With ventilation we don’t get 100% turnover of the air from the atmosphere in the lungs

• 100mmHg oxygen is leftover in lungs after all factors

• Diffusion drives oxygen into the cell because there's less oxygen in the cell than in the blood

• Once oxygen enters the cell partial pressure of oxygen decreases and carbon dioxide increases

• Partial pressure of oxygen throughout the body is changing and this drives flows

Flow of O2 along the capillaries

• O2 diffuses from alveoli to blood

• Doesn’t take entire capillary length to do the diffusion

• Less and less diffusion as you move across the capillary

• Gradient decreases so diffusion rate decreases

• P1 in alveoli is higher than P2 in pulmonary capillaries, drives flow

Flow for CO2 along the capillaries

• We start with high CO2 and offload it so it decreases

• CO2 diffuses from blood to alveoli

• P1 in pulmonary capillary is higher than P2 in alveoli drives flow

Peripheral chemoreceptors

Found in carotid bodies and aortic arch. Direct contact with blood. Sensitive to changes in PO2, PCO2 (indirectly), pH (H+). Afferent feedback sent to medullary respiratory control center, which stimulates changes in ventilation.

Central chemoreceptors

Located in the medulla oblongata (part of the brain). Not in direct contact with blood, it is separated by the blood brain barrier. Respond to changes in pH of the cerebral spinal fluid (CSF).

They are H+ sensitive, but H+ does not occur in the blood brain barrier. CO2 does cross the blood-brain barrier, but does not stimulate chemoreceptors.

Bicarbonate buffering

Maintains blood pH by allowing central chemoreceptors to sense the blood pH.

• The more CO2 that enters, the more hydrogen that is produced, which is sensed

• This is a near-equilibrium reaction so can occur in both directions, increased H+ results in increased CO2 and increased CO2 results in increased H+

Control of ventilation feedback mechanism

• When oxygen drops, ventilation is increased

• increasing ventilation increases alveolar PO2, which increases ∆P for O2 into the blood

• When CO2 rises, ventilation is increased

  • Increasing ventilation decreases alveolar PCO2, this increases the ΔP for CO2 diffusion out of the blood

Important terminologies for ventilation rate

Minute Ventilation: VE in L/min (liters per minute)

Tidal Volume: VT in L (volume per breath)

Breathing Frequency: fB in breaths/min

VE = VT x fB

Alveolar Ventilation = (Tidal Volume – Dead Space) x breath frequency

Components of the cardiovascular system

1. Heart (Cardiac muscle): Acts as a high pressure pump which allows blood to flow down Pressure Gradient (ΔP)

2. Vascular System:

   1. Arteries – O2 & nutrient rich - blood flows away from heart to the body

   2. Veins - O2 & nutrient poor (waste rich) - blood flows to heart after it goes throughout the body to be reoxygenated

Order of blood flow in the heart

1. Blood enters the heart through the inferior and superior vena cava

2. Then continues into right atrium, travels through right AV tricuspid valve into the right ventricle

3. From the right ventricle blood moves through the semilunar valve, into the pulmonary artery

4. Pulmonary artery brings oxygen/nutrient poor blood to the lungs to be oxygenated and have gas exchange

5. After the lungs, blood comes to the heart through pulmonary veins, then enters left atrium, which is then pumped through left AV bicuspid valve into left ventricle

6. Left ventricle is very strong and creates high pressure gradient to push blood from left ventricle through aortic semilunar valve into aorta, which travels blood throughout the body

Heart

The heart is found in the thoracic cavity. Heart is size of fists and weighs 250-300grams. Heart is surrounded by the pericardium.

Pericardium

membranous sac that surrounds the heart, which lubricates heart to decrease friction among other body parts when the heart pumps.

Pericarditis

condition in which there is inflammation of the pericardium

Blood vessels

Arteries: larger smooth muscle layer to allow for contraction. Bring oxygenated blood away from heart to other body parts

Veins: have valves, bring oxygen/nutrient poor blood back to the heart

• Valves allow blood to move against gravity back up to the heart

Order of blood flow in the body

• From the left ventricle of the heart, the blood enters the aorta then the arteries

• From the arteries there are smaller vessels called arterioles which have a high resistance

• Capillaries are sites for blood to exchange nutrients and oxygen with tissues

• Venules are small converging vessels

• Veins are larger converging vessels

• Blood enters the heart at the vena cava

• This system is a close loop system; the blood does not leave the body vessels intentionally

Pulmonary arteries vs pulmonary veins

Pulmonary arteries: oxygen poor, but still moves blood away from heart to lungs

Pulmonary vein: oxygen rich but moves blood towards the heart

Blood composition

• Blood is 55% plasma; least dense layer

  • Fluid and solutes that exist in blood

• Buffy coat; contains leukocytes and platelettes, only about 1%

• Erythrocytes: red blood cells, very important for oxygen and co2 transport, about 45%

Sickle cell anemia

Inherited disease in which blood cells have a reduced capacity to bind oxygen, making it difficult to deliver to the body. Blood cells have a sickle shape.

How does the heart receive blood?

Arteries on the heart called coronary arteries supply blood to the heart to allow it to function and work

Heart attack

When coronary arteries are blocked (usually from plaque build up) a heart attack occurs. Blood can no longer continue through these arteries to supply heart muscles with oxygen and nutrients, the muscles of the heart stop functioning.

Blood flow flow model

• vascular resistance and conductance are opposites

• The heart beating/contraction creates the high pressure for inflow for blood into the arteries

  • the ventricle gets smaller, and blood is pushed out

• The arterioles create resistance to blood leaving (outflow) the arteries