Circulatory System Functions

• The circulatory system transports blood and dissolved substances throughout the body.
• The heart pumps blood and substances through blood vessels.
• The heart, blood, and blood vessels comprise the circulatory system.

Functions

• Delivers oxygen to cells, especially muscle cells.
• Provides nutrients, like glucose, to cells.
• Removes waste products, such as lactic acid, from cells.
• Eliminates carbon dioxide from the body.
• Transports hormones to tissues to regulate their function.
• Regulates body temperature.

Double Circulatory System

• The circulatory system consists of two fully enclosed circuits.

The Heart

• The heart has four chambers: two atria (right and left) and two ventricles (right and left).
• Veins carry blood into the heart.
• Arteries carry blood away from the heart.

Heart Function

• The heart muscles relax, allowing blood to flow into the atria.
• The atria contract, opening valves for blood to flow into the ventricles.
• The valves close to prevent backflow as the ventricles contract, forcing blood out of the heart.
• The atria relax and refill with blood as the cycle repeats.

Blood Vessels

Arteries

• Arteries and arterioles carry blood away from the heart.
• Elastic fibers allow arteries to stretch under pressure.
• Thick muscles contract to propel blood.
• The aorta is the largest artery.

Veins

• Veins and venules carry blood toward the heart.
• Valves prevent backflow.
• Body muscles squeeze veins to push blood along.
• The vena cava is the largest vein.

Capillaries

• Capillaries connect arteries and veins.
• Material exchange occurs between blood and body cells through capillaries.
• Capillary walls are one cell thick.
• A capillary bed is a collection of capillaries.

Blood Composition

• Blood contains digested food, white blood cells, waste (urea), platelets, hormones, plasma, carbon dioxide, oxygen, and red blood cells.
• Humans have approximately 4-5 liters of blood, making up about 8% of body weight.

Red Blood Cells

• Red blood cells are round, flat discs containing hemoglobin for oxygen transport.
• They can change shape to squeeze through capillaries.

White Blood Cells

• The main types are lymphocytes and macrophages.
• Macrophages ingest microorganisms.
• Lymphocytes produce antibodies or antitoxins to fight disease.

Platelets

• Platelets are cell fragments that activate to form blood clots when encountering collagen in broken blood vessels.

Plasma

• Plasma is a straw-colored liquid carrying cells, platelets, carbon dioxide, glucose, amino acids, proteins, minerals, vitamins, hormones, and waste materials.
• It makes up 65% of blood volume.

Blood Pressure

• Blood pressure drives blood through the circulatory system, measured as systolic and diastolic pressure.
• Normal blood pressure is around 120/80 mmHg.
• Systolic pressure occurs when blood is ejected from the ventricles.
• Diastolic pressure occurs when ventricles relax.
• The "Lub-Dub" sound is the heart valves snapping shut; "Lub" is the ventricles contracting (A-V valves), and "Dub" is the aortic and pulmonary valves closing.

Cardiac Output

• Cardiac output (Q) is the amount of blood pumped out of the left ventricle.
• Heart Rate (HR) is the average beats per minute (bpm) out of the heart
• Stroke volume (SV)
• Maximum Oxygen Uptake/Aerobic Power Max VO2 is the amount of O2 the body uses per minute
• Max VO2 = max Q x a-vO2 diff, measured in liters per minute (around 6 L/min) or ml/kg/min when considering body weight.
• A moderately trained athlete has a score around 50ml /kg/ min.
• The highest levels recorded are in the vicinity of 93 ml /kg /min. Lance Armstrong’s was 85ml/ kg/min

Respiratory System

Primary Functions

• Ventilating the lungs supplies oxygenated blood to the body.
• Exhaling from the lungs removes carbon dioxide from the blood.

Respiratory Process

• Air flows from the mouth/nasal cavity through the pharynx and larynx to the trachea.
• Air moves to the bronchi tubes entering the lungs.
• Air enters bronchioles within the lungs.
• Oxygen from the alveoli passes into the bloodstream, while carbon dioxide passes from the blood into the alveoli to be exhaled.

Parts of the Respiratory System

Nasal Cavity

• Warms incoming air via a capillary network.
• Filters incoming air with hairs.

Pharynx

• The throat carries air, food, and fluid.

Larynx

• Generates sound, pitch, and volume (voice box).
• Houses vocal folds/chords.

Trachea

• Directs air towards the lungs.
• Mucous lining traps foreign material.
• Cilia (microscopic hairs) filter the air.
• Supported by cartilage rings.

Bronchi

• Two tubes branching towards the lungs, similar in structure and function to the trachea.

Bronchioles

• Further branches of the bronchi, dividing like tree branches until they reach alveoli.

Alveoli

• Air sacs that increase the surface area for gas exchange, surrounded by capillaries where oxygen and carbon dioxide transfer occurs.

Respiratory Process Summary

• Inhale: Nasal cavity → Pharynx → Larynx → Trachea (filtered by cilia) → Bronchi → Bronchioles → Alveoli (gas exchange).
• Exhale: Reverse of the above process.

Diaphragm

• Flat, dome-shaped muscle at the bottom of the chest cavity.
• Functions in breathing.

Inspiration

• Diaphragm pulls down, increasing chest cavity space.
• Intercostals pull the rib cage up and outwards.

Expiration

• At rest, muscles relax, and gravity/pressure forces air out.
• During exercise, abdominals pull the rib cage down, decreasing chest cavity size for forceful expulsion.

Respiratory Measurements

• Total lung capacity (TLC): the volume of air in the lungs at maximal inflation, measured in litres
• Average TLC in healthy adult men: 6.0L, women: 4.2L
• Ventilation (V) is the amount of air breathed per minute (Litres)
• Tidal Volume (TV) is the amount of air that is inspired or expired per breath, normally around 500ml
• Respiration rate (RR): breaths in or out per minute, 12 on average
• V = TV x RR
• Residual Volume (RV) is the amount of air left in the lungs after a maximal exhalation, and can never be expired. The trachea, bronchi and other spaces can never fully collapse.

Interesting Facts

• About half a litre of water is lost daily through breathing.
• Yawning increases oxygen to the lungs.
• The right lung is larger than the left.
• 7.3 Litres of air are breathed in a minute.
• People under 30 intake double the oxygen compared to those 80 years old.