Understanding Blood Circulation, Kidneys, and Waste Removal

Blood Circulation and Waste Removal Processes

The exchange of substances occurs between blood plasma and tissue cells through a network of arteries and veins.

The Heart's Chambers

Atria

The atria receive blood from the veins coming from the body's organs. They communicate with the ventricles through valves (mitral and tricuspid).

Ventricles

The ventricles are connected to arteries that pump blood from the heart throughout the body. Semilunar valves between the ventricles and arteries prevent backflow.

Blood Flow Dynamics

Blood always flows in the same direction: from veins to arteries.

• Atrial Systole: Atrial contraction pushes blood into the ventricles.
• Ventricular Systole: Ventricles contract, closing the mitral and tricuspid valves, and forcing blood into the arteries. The volume of blood entering the arteries causes the sigmoid valves to close, preventing backflow.
• Diastole: Ventricles relax, opening the mitral and tricuspid valves to receive blood from the atria.

Circuits of Blood Flow

Pulmonary Circuit

Blood from the right ventricle is pumped to the lungs for gas exchange. Oxygenated blood returns to the left atrium via the pulmonary veins.

Systemic Circuit

Oxygenated blood from the left ventricle is pumped through the aorta to all organs and tissues. Gas exchange occurs in the capillaries. Deoxygenated blood returns to the right atrium via the vena cava.

Waste Removal

Carbon Dioxide

CO2 is transported in blood plasma to the pulmonary alveoli for expulsion during exhalation.

Nitrogenous Waste

Other waste products are filtered by the kidneys and excreted as urine and sweat.

The Kidneys and Urinary System

Kidneys

Nephrons within the kidneys filter blood, collecting waste substances to produce urine.

Urinary Tract

The urinary tract carries urine from the kidneys to the exterior.

• Ureters: Transport urine from the kidneys to the bladder.
• Bladder: Stores urine.
• Urethra: Carries urine from the bladder to the outside.

Nephron Function

Nephron Components

• Bowman's Capsule: Surrounds a capillary ball (glomerulus).
• Renal Tubule: A thin, U-shaped tube.
• Collecting Duct: Receives urine from multiple nephrons.

Kidney Function

The kidneys filter blood plasma, reabsorbing useful substances and eliminating waste.

• Filtration: Components of blood pass from the glomerulus into Bowman's capsule.
• Reabsorption: The renal tubule reabsorbs useful substances from the filtrate back into the blood, while waste products remain.

The fluid that remains becomes urine, which travels through the collecting duct to the renal pelvis. By producing urine, the kidney functions as an excretory organ and regulates the composition of the internal environment.