3.4 Circulatory System

2026-04-20 21:34

Status: #new

Circulatory System

The circulatory system transports nutrients and wastes from cells around the body
It can regulate internal body temperature (~ $37^{\circ} C$ )
Delivers hormone signals between organs
Protects against blood loss during injury and prevents infections from spreading
There are 3 main components:
- Blood
- Heart
- Blood Vessels
Simple Organisms
- They absorb nutrients from aquatic environments, by diffusing it into the body.

There are 4 main components
- Plasma (~55%)
- Erythrocytes (~44%)
- Leukocytes (~1%)
- Thrombocytes (~1%)
Blood is not a uniform type of fluid! It is dependent on its organism. (It can be different colours in other organisms), and exists to transport nutrients.

Plasma is made out of primarily water and dissolved nutrients
- It's a balance of fluid, salts and pH (~Slightly Alkaline)
- Essentially the fluid in the blood

Red blood cells
Consist of a biconcave shape due to their lack of nucleus
- However this means a increased surface area to carry nutrients and waste
The red colour is indicative of the protein hemoglobin
- Heme means an iron bound to the centre of a global structure
- Globin just means a type of protein structure
Oxygen binds to the heme group so that they can be transported into the body
Hemoglobin also carries CO2 waste from cells
- Carbon Dioxide binds to one end of the globin molecule rather than at the Fe ions
- CO2 waste is dissolved in plasma
- It reacts with Water to produce a pH balancing bicarbonate molecule
Deoxygenated blood are darker
- When observed through the naked eye, the skin makes the dark red blood look blue
Carbon Monoxide is dangerous as it is polar and sticks to red blood cells
Anemia is caused by iron deficiency, which leads to low levels of red blood cells

Leukocytes are also known as white blood cells.
There are 5 types and 2 groups
- Monocytes and Lymphocytes are known as Agranulocytes
  - Agranulocytes do not have granules (dots)
- Basophils, Eosinophils and Neutrophils are Granulocytes
  - Granulocytes have granules (dots)
During an infection, Leukocytes double in order to increase the immunological response.

Known commonly as platelets
These are tiny cell fragments, which help in blood clot formation.
- Produced in the bone marrow, and clump up at the site of an injury

The flow through the heart has:
- 4 Chambers
- 4 Valves
- 2 Arteries
- 2 Veins
The Atris (Atrium) are chambers blood enters at the top
Ventricle are chambers blood if pumped out at the bottom
Atrioventricular Valves
- Found between atria and ventricles
Semi-lunar valves
- Blood leaves the ventricles
Pericardial sac
- This is a membrane around the heart that contains a small layer of fluid to allow the smooth pumping of the heart, essentially a lubricant layer.
- Also prevents the heart from filling
Septum
- This tissue separates the left and right sides of the hear
- Ensures that oxygenated and deoxygenated blood do not mix
Open circulatory system
- Blood flows in and out in all directions
Closed Circulatory System
- Blood doesn't leak (uni-directional flow)
Chordae Tendinae
- Also known as heartstrings, they help maintain the atrioventricular valves and keep the heart closed

Stethoscope
- Listens to the sound and rhythm of the valves closing
Electrocardiogram (EKG)
- Measures electrical nerve signals used to control the heart
- Pacemakers can be installed above the heart in individuals who do not have sufficient electrical signals
Blood Pressure
- There are two indicators in blood pressure (measured in mm Hg)
- Systolic Pressure is the "peak" pressure in a single heart beat
  - This is the pressure that stops blood flow
- Diastolic is "minimum pressure" in a single heart beat
  - This is the pressure after blood is allowed to flow
- The force applied by the blood open blood vessel walls
- This is measured using a sphygmomanometer
  - A normal blood pressure is 120/80
MRI's
- Can detect aneurysms (This is a weak spot in a artery that can rupture, caused by pressure pushing against a weakened section of a blood vessel)
- Surgery is needed to patch or replace the damaged blood vessel section.
Leukemia
- Blood cancer in the bone marrow that produces abnormal amount of blood cells
- Requires a bone marrow transplant
Circulatory Transplant
- Replace parts of the heart with artificial parts

Allow the visualization of plaque (a fat, calcium and fibrous deposit)
- This is a hardened structure impeding blood flow that needs to be removed as it blocks arteries.
Angioplasty
- A procedure to widen or narrow arteries blocked arteries
Coronary Bypass
- Creates a new path for blood flow using healthy blood vessels from other parts of the body
- A bypass uses synthetic blood vessels that are grafted onto the blocked blood vessel

Arteries carry blood away from the heart
Pulmonary Arteries carry deoxygenated blood
Aorta carries oxygenated blood.
- The Aorta is larger due to pumping higher volume
Thick walls to withstand the pressure of blood leaving the heat.
- Eventually become Aterioles, that are more narrow (Blood spreads out to maximize surface area)

Veins return blood to the heart
Pulmonary veins carry oxygenated blood
Vena cava carry deoxygenated blood
Valves may be found within veins to prevent blood from flowing backwards
- These are one way gates
Narrow venules join to create wider veins

Thinnest of all blood vessels
Are one cell thick (this minimizes distance to other cells)
- The diameter means that erythrocytes can only flow through single file
This is where nutrient and waste exchange occur