Understanding the Human Heart

The Heart

• Primary role is to circulate blood throughout the body.
• Human hearts are part of a double circulatory system.
• Blood passes through the heart twice in each complete circuit.
• The sequence is: right side of the heart to lungs, then left side of the heart to the body, and back to the heart.
• Heart walls consist mainly of muscle that contracts to pump blood.
• A group of cells in the right atrium acts as a natural pacemaker for resting heart rate.
• When these cells malfunction and cause an irregular heart rate, an artificial pacemaker can be implanted.

Key Heart Structures and Blood Flow

• Ventricles are the larger chambers.
• The right ventricle pumps blood to the lungs.
• The left ventricle pumps blood to the entire body.
• Atria are smaller chambers that receive blood.
• The vena cava and pulmonary vein channel blood into the ventricles.
• The aorta is the main artery carrying blood out of the left ventricle to the body.
• The vena cava is a major vein returning blood from the body to the right atrium.
• The pulmonary artery transports blood from the right ventricle to the lungs.
• The pulmonary vein carries blood from the lungs back to the left atrium.

Blood Vessels

• Blood is confined to vessels, except in cases of injury.
• Arteries, capillaries, and veins are the three types of blood vessels.
• Blood flow sequence: arteries to capillaries to veins, then veins back to the heart.
• Arteries transport blood at high pressure and have thick, elastic walls.
• Capillaries facilitate exchange with cell walls that are only one cell thick.
• Veins return blood to the heart at low pressure, thus walls are thinner than arterial walls.
• Veins contain valves to prevent backflow.

Key Blood Vessel Details

• Arteries carry blood away from the heart under high pressure.
• Capillaries facilitate substance exchange with their thin walls.
• Veins return blood to the heart with relatively low pressure.
• The coronary blood vessels supply the heart muscle.
• They branch off the aorta immediately after it departs the heart.

Lungs

• Lungs facilitate gas exchange in humans and mammals.
• Inhalation brings air through the trachea (windpipe) to bronchi to each lung.
• Air finally enters alveoli.
• Contraction of the diaphragm and intercostal muscles allows inhalation.
• These muscles relax to facilitate exhalation.
• Lungs have a short diffusion pathway, large surface area, and good blood and air supplies enhancing efficient gas exchange.

Blood Composition and Function

• Blood is a tissue consisting of plasma and suspended cells.
• Plasma constitutes over half the blood's volume
• Red blood cells, white blood cells, and platelets are plasma components.
• Red blood cells primarily carry oxygen.
• White blood cells combat infection.
• Platelets are involved in blood clotting.

Blood Components Defined

• Plasma is the liquid part of blood.
• It is mostly water and contains dissolved substances like glucose, proteins, ions, and carbon dioxide.
• Red blood cells are disc-shaped cells contain haemoglobin.
• Haemoglobin binds to oxygen for movement from lungs to tissues.
• White blood cells are immune cells that combat pathogens.
• Platelets are cell fragments involved in clotting to reduce hemorrhaging.
• A clot is a solid mass of blood that forms at an injury site, halting blood loss.

Red Blood Cells

• Red blood cells are disc-shaped for increased surface area.
• They don't have a nucleus or other organelles.
• They mainly consist of haemoglobin, facilitating oxygen transport.

Platelets and Clotting

• Platelets are deliberately produced cell fragments.
• They initiate the clotting process at wound sites.
• They create a clot, which blocks injured blood vessels.
• Clots facilitate healing while preventing excessive blood loss.

White Blood Cells

• White blood cells are part of the immune system, fight communicable illnesses.
• They have large nuclei and can change shape to pass through capillary gaps.
• They engulf microorganisms.

Plant Tissues and Transport

• Leaves contain various tissues that work together as part of a transport system.
• Substances circulate throughout the plant.
• The leaf contains xylem and phloem vessels.
• The stomata are pores that facilitate gas exchange, including water vapor.
• Plants absorb water through roots and maintain water flow via water evaporation from leaves.
• The continuous upward flow of water is the transpiration stream.
• Water vapor loss from leaves is transpiration. Transpiration increases with higher temperatures, lower humidity, higher air flow, and higher light intensity.

Terms for Plant Anatomy and Processes

• Epidermal tissue covers the surface of a plant.
• Palisade mesophyll is the leaf tissue where photosynthesis occurs.
• Spongy mesophyll facilitates gas exchange.
• Xylem moves water and mineral ions up from the roots.
• Phloem transports dissolved sugars.
• Meristem is a type of plant tissue contains stem cells that differentiate into various cell types.
• Guard cells form stomata and regulate gas exchange.
• Transpiration water loss from leaves.

Xylem and Phloem Details

• Xylem is made of dead cells forming continuous tubes.
• They're reinforced by lignin and move water and minerals.
• Phloem consists of living cells arranged end-to-end to form tubes.
• Phloem transports dissolved sugars via translocation.

Stomata and Guard Cells

• Stomata allow carbon dioxide entry for photosynthesis.
• Guard cells regulate stomatal opening, conserving water in dry conditions.