Transport in Animals

Blood Plasma to Capillaries: Blood plasma is forced out of the capillaries due to high pressure on the arterial side.
Tissue Fluid Formation: This forced-out fluid is called tissue fluid, containing oxygen, glucose, ions, etc.
Diffusion into Cells: Oxygen and glucose diffuse from the tissue fluid into the cells.
Waste Removal: Waste products like carbon dioxide diffuse out of the cells into the tissue fluid.
Fluid Reuptake: The tissue fluid returns to the capillaries due to low pressure on the venous side.
Efficiency: The difference in pressure between arteries and veins makes tissue reuptake efficient.

Oxygen: Oxygen diffuses from the blood into tissues following a concentration gradient (high to low).
$O_2$ moves from blood to tissues
No energy input.

Glucose: Glucose moves into tissues, sometimes against the concentration gradient.
Mechanism: Sodium-glucose co-transporters facilitate the passive movement of glucose.
Indirect Passive Transport: Energy is used to actively pump sodium ions.
Sodium ions create an area of high concentration, and then glucose and sodium move together into an area where there's a low concentration of sodium.
Glucose moves from blood to cells alongside sodium.

Carbon Dioxide: Carbon dioxide diffuses from cells into the blood following a concentration gradient (high to low).
$CO_2$ moves from tissues to blood
Moves from high to low concentration to maintain movement.

About 85% of the fluid forced out of capillaries returns through the capillary network and veins.
15% of the fluid drains into the lymphatic system and is called lymph.
Lymph eventually drains back into the heart and circulatory system.

High pressure needed to pump blood to the body.
Lower pressure needed in the lungs for efficient oxygen diffusion from alveoli to capillaries.
High pressure in lung capillaries would prevent oxygen diffusion.

Fish do not need a double circulatory loop.
Blood is sent from the heart to the gills at high pressure.
Water pressure outside the gills balances the blood pressure, preventing damage to blood vessels.

Right Side:
- Vena Cava: Blood enters the heart through here.
- Right Atrium: One of the chambers where blood flows into.
- Right Ventricle: Blood flows from the right atrium into this bottom chamber.
- Atrioventricular Valves: Valves that open and shut to allow blood flow between the atria and ventricles.
Lungs: Blood picks up oxygen and returns through the pulmonary vein.
Left Side:
- Left Atrium: Blood flows into this chamber from the lungs.
- Atrioventricular Valves: Just like the right side.
- Left Ventricle: Blood flows in here. When it squeezes, it forces blood through the aorta to the rest of the body.
Pulmonary Artery: From the right ventricle and goes to the lungs, also has valves called semilunar valves that open and shut, allowing blood flow to the lungs.
Aorta: Big blood vessel getting blood to the body, consists of semilunar (aortic) valves that close to prevent backflow.

Muscular walls of the atria are thinner than the ventricles
The muscular wall of the left ventricle is thicker than the right ventricle, since it has to pump blood all the way to the body.
Septum: Separates the right side from the left to prevent oxygenated and deoxygenated blood from mixing.
Coronary Arteries: Branch off the aorta and carry oxygen-rich blood to the heart tissue itself.
SA Node: Located in the right atrium, it initiates the heartbeat. Also known as the pacemaker.
AV Node: Located in the right atrium. It has a function in getting the heartbeat signal to these ventricles.

Septum: Prevents mixing of oxygenated and deoxygenated blood.
Coronary Arteries: Bring oxygenated blood to the heart tissue.
SA Node (Pacemaker): Initiates the heartbeat.
Atria: Collect and contract to squeeze blood into the ventricles.
Ventricles: Contract to pump blood into the arteries.
Atrioventricular Valves (AV Valves): Prevent backflow of blood into the atria when the ventricle contracts.
Semilunar Valves (Pulmonary/Aortic Valves): Prevent blood from flowing back into the ventricle when the ventricle is relaxed.
AV Node: Helps to get the heartbeat signal to the ventricles.

Intercalated Discs: Form connections and passages and help form connections and passages of electrical signals.
Cell Branching: Helps facilitate coordinated contractions throughout the heart tissue.
Myogenic Contractions: Cardiac contractions start on their own without nerve input.

A cardiac cycle happens about 70 times per minute and consists of $Systole$ (contraction) and $Diastole$ (relaxation).
Systole sounds likes squeeze and diastole sounds like dilate, this is useful in helping you remember their meanings.

Atrial Contraction (Systole): Forces AV valves to open, allowing blood to flow into the ventricles.
- Atria are in systole, ventricles are in diastole.
- There is about a one second gap due to the SA and AV node firing at different times.
Ventricular Contraction (Systole): Slams AV valves shut, preventing backflow to the atria, and forces semilunar valves open, allowing blood to go to the arteries.
- Ventricles now go into diastole.
- Atria meanwhile fill with blood.

Pressure measured in mmHg (millimeters of mercury).
Pressure tracked in the atrium, ventricle, and artery.
When the pressure increases, it's under systole, and when the pressure decreases, it's under diastole.
Arteries are always going to be at relatively high pressure to maintain bloodflow. Additionally, the pressure increases when the ventricles contract, resulting in a pulse.
Ventricles are always under higher pressure than atria for bloodflow purposes.
When one chamber is contracting, the other one must relax in the cardiac cycle.