Week 5: Blood, Breathing, and Gas Exchange

Oxygen and Carbon dioxide transport

STEPS:

1.) oxygen exchange @ alveolar capillary interface

2.) oxygen transport

3.) Oxygen Exchange @ cells

4.) CO2 exchange @ cells

5.) CO2 transport

6.) CO2 exchange @ alveolar capillary interface

Partial pressue of oxygen

Lungs: 100 mmHg

Tissues: 40 mmHG

Partial pressure of Carbon Dioxide

Lungs: 40 mmHG

Tissues: 46 mmHG

Causes of Low Alveolar PO2

1) Inspired air has abnormally low oxygen content (altitude)

2) Alveolar ventilation is inadequate (decreased lung compliance/increased airway resistance/overdose of drugs)

2 ways to carry oxygen

1.) dissolve in plasma >98%

2.) Bind to Hb <2%

Hb carries 4 oxygen

3 ways to carry CO2 in blood

1.) dissolve in plasma 7%

2.) Bind to Hb 25%

3.) HCO3- 70%

oxygen-hemoglobin dissociation curve (right shift)

1. decreased pH and affinity

2. Increased temperature, CO2, 2,3 DPG, H+

oxygen-hemoglobin dissociation curve (right shift)

1. Increased pH and affinity

2. Decreased temperature, CO2, 2,3 DPG, H+

irritant receptors in lungs

tell brain to increase respiratory rate to get irritants out

- bronchoconstriction

- sneezing

- coughing

Control of Ventilation

Primary control centers for breathing located in the medulla and the pons

Chemoreceptors (stimulated by acidic pH, and PaCO2)

Irritant receptors: epithelium of conducting airways

Stretch receptors: protective

Breathing influenced by

- emotions

- chemoreceptors, leader in controlling breathing

Emphysema

destruction of alveoli, reduces surface area available for gas exhange

fibrotic lung disease

Thickened alveolar membrane slows gas exchange. Loss of lung compliance may decrease alveolar ventilation

pulmonary edema

Fluid in interstitial space increases diffusion distance. Arterial PCO2 may be normal due to higher CO2 solubility in water.

Asthma

increased airway resistance decreases alveolar ventilation

Hypoxia

Impaired diffusion of gases between the alveoli and blood

hypoxic hypoxia

decreased arterial PO2

anemic hypoxia

decreased total amount of O2 bound to hemoglobin

ischemic hypoxia

decreased blood flow

histotoxic hypoxia

failure of cells to use O2 because cells have been poisoned

Movement of gasses from air into a liquid is directly proportional to:

- pressure gradient

- solubility

- temperature

Diffusion of Gasses

follow ficks law (surface area x concentration gradient x membrane permeability / membrane thickness)

Composition of blood

plasma, red blood cells, white blood cells, platelets

red blood cells (erythrocytes)

transport oxygen and carbon dioxide

White bloodcells (leukocytes)

Defend against infection

Platelets (thrombocytes)

blood clotting, stop bleeding

Hematopoiesis

process of making blood cells

Erythropoietin (EPO)

hormone secreted by the kidneys; stimulates red blood cell formation

Thrombopoietin (TPO)

a hormone produced by the liver that stimulates the formation of platelets from megakaryocytes

Hematocrit

Ratio of red blood cells to total blood volume

- MEN: 40-54%

- WOMEN: 37-47%

Red blood cell formation

erythropoiesis requires iron. RBCs live for 120 days. Hb components are recycled.

STEPS:

1.) iron from diet

2.) iron absorbed via active transport

3.) transferring moves iron into plasma

4.) liver stores excess iron as ferritin

5.) bone marrow uses iron to make hemoglobin

6.) spleen converts Hb to bilirubin

7.) liver metabolizes bilirubin, and excretes it as bile

8.) Bilirubin metabolites excreted in urine and feces

Spleen

destroys old red blood cells, makes bilirubin

Jaundice

Elevated levels of bilirubin

Erythrocytes places in hypotonic solution will

Swell, water rushed in

Erythrocytes places in hypertonic solution will

Shrink, water rushed out

Normal Red Blood Cell

biconcave shape

Causes of Anemia

RBC blood loss & Decreased Production of RBC

hemolytic anemia

anemia caused by the destruction of red blood cells

-Hereditary, example sickle cell

- Acquired via infection, example malaria

aplastic anemia

failure of blood cell production in the bone marrow, can be caused by certain drugs or radiation

- Inadequate intake of nutrients, decreased iron, B12, folic acid

sickle cell anemia

a genetic disorder that causes abnormal hemoglobin, resulting in some red blood cells assuming an abnormal sickle shape. Glutamate is replaces with valine as the 6th amino acid on chain

Hemostasis

blood clotting and tissue repair

STEPS:

1.) Vasoconstriction - reduces blood flow to site of injury

2.) Platelets aggregate into loose platelet plugs (temporary solution)

3.) Clot: reinforced platelet plug (permanent solution)

platelet plug formation

1. exposed collagen binds and activates platelets

2. release of platelet factors

3. factors attract more platelets

4. platelets aggregate into platelet plug

coagulation and fibrinolysis

Fibrinogen and thrombin activate Plasma, which dissolves the clot leading to fibrinolysis

Fibrin

protein that forms the basis of a blood clot

Thrombin

enzyme that converts fibrinogen to fibrin during coagulation

respiratory system functions

- exchange gasses (via alveoli)

- homeostatic regualtion (by retaining/exchanging CO2)

- protection from unhaled pathogens/irritants

- vocalization

Bulk Airflow

- high pressure to low pressure

- muscular pump creates pressure gradient (diaphragm)

-resistance to flow influenced by tube diameter (vessel radius influences blood flow resistance)

external respiration

the exchange of gases between the atmosphere and the blood

internal respiration (aerobic)

intracellular reaction of oxygen molecules to produce CO2 H20 and ATP

Quiet Breathing

Passive

muscles of inspiration

-sternocleidomastoid

- scalenes

- external intercostals

- diaphragm

- all contract

muscles of expiration

internal intercostals and abdominal muscles

- no muscle contraction

- collapse our lungs

Pleural sac

- wraps around lungs

- 2 membranes

Inner attached to lungs

Outer attached to thoracic wall

pleural fluid function

- lubricates opposing membranes so they can slide across one another as lungs move

- holds lungs tight against the thoracic wall

branching of airways

- larynx (lowest SA)

- trachea: c-shaped rings help keep airway open

- primary bronchus

- secondary bronchus

- bronchiole

- alveoli (highest SA) : 80-90% surrounded by capillaries

Alveoli structure

- clustered @ end of bronchioles

- make up bulk of lung tissue

type 1 alveolar cells

thin, allow gas exchange

type 2 alveolar cells

secrete surfactant

Surfactant

chemical produced in the lungs to maintain the surface tension of the alveoli and keep them from collapsing, contains proteins and phospholipids

Dalton's Law

Total pressure equals sum of partial pressures.

Boyle's Law

if you decrease the volume of a container of gas and hold the temperature constant, the pressure from the gas will increase

Gas theory

Gas moves from high pressure to low pressure

spirometer

Measures how much air moving in/out of the body

vital capacity

the maximum amount of air that can be exhaled after a maximum inhalation

Functions of the upper airway

warm, filter, humidify inspired air

air flow

directly proportional to alveolar pressure

inversely proportional to resistance

alveolar pressure

pressure within the lungs

intrapleural pressure

pressure within the pleural cavity, pleural fluid

inspiration

Alveolar pressure < atmospheric pressure

- alveolar pressure is lower, atmospheric pressure drawn in, lung volume decreases = pressure dropped

expiration

- Diaphragm contraction causes 60-70% of the inspiratory volume

- rib cage creates the remaining 25-40%

Pneurmothorax

collapsed lung, pleural pressure: 3 mmHg

Law of Laplace

Surfactant reduces surface tensions, if have the same surface tension, small will have higher pressure

compliance

- ability of the lung to stretch

- high compliance: stretches easily

- low compliance: requires more force can lead to restrictive lung disease

* important for lung function

Elastance

ability to return to resting volume when stretching force is released

total pulmonary ventilation

ventilation rate x tidal volume

alveolar ventilation rate

ventilation rate x (tidal volume - dead space volume)

Hyperventilation

- increased respiratory rate and/or volume without increased metabolism (ex blowing up balloon)

- high 02 low CO2

hypoventilation

decreased alveolar ventilation

High C02 Low O2

(shallow breathing, asthma, restrictive lung disease)

Normal Ventialtion

- O2: 100 mmHG

- CO2: 40 mmHG

Normal ventilation values

total pulmonary ventilation: 6 L/min

total alveolar ventilation: 4.2 L/min

maximum voluntary ventilation: 125-170 L/min

respiration rate: 12-20 breaths/min

newborn respiratory distress syndrome

Premature babies

Inadequate surfactant concentrations

Results in stiff lungs and alveoli that collapse

Ventilation

Local control matches ventilation and perfusion