GCSE Biology - Structure of the Kidneys - (Kidneys Part 2/3)

New Section

In this video, we will explore the anatomy of the urinary system, with a focus on the structure of the kidneys.

Anatomy of the Kidneys

• The kidneys have three main roles: removing waste products from the blood, regulating ion levels in the blood, and controlling water balance.

• Blood enters the kidneys through renal arteries and exits through renal veins.

• The kidneys produce urine from filtered fluid, which then passes through ureters and is stored in the bladder until it is eliminated through the urethra.

Structure of Nephrons

• Nephrons are tiny structures within the kidneys responsible for urine production.

• A cross-section of a kidney reveals numerous nephrons.

• Each nephron consists of a tubule (yellow) and blood vessels (red).

Filtration Process

• Filtration occurs at the glomerulus, where liquid from blood is forced into Bowman's capsule.

• Only small substances like water, amino acids, urea, glucose, and ions can be filtered. Larger molecules like cells or proteins cannot pass through.

• Approximately 20% of plasma in the blood is filtered at this stage.

Selective Reabsorption

• As fluid passes along tubules, useful substances such as glucose and amino acids are reabsorbed back into blood vessels.

• Water and ions are also partially reabsorbed based on their importance to bodily functions.

• Urea is not reabsorbed since it is considered waste.

Naming Parts of Nephron

• After Bowman's capsule comes the proximal convoluted tubule.

• Next is the loop of Henle followed by the distal convoluted tubule.

• Finally, there's a collecting duct that receives fluid from multiple nephrons. Any fluid that leaves this duct is classified as urine.

Urine Elimination

• Urine passes down the ureter to the bladder for storage.

• When ready, it is released as waste through the urethra.

New Section

This section discusses the flow of urine and its elimination from the body.

Flow of Urine

• Urine travels from the collecting duct down the ureter.

• It is then stored in the bladder until elimination.

Elimination Process

• When ready to eliminate urine, it passes through the urethra.

• The bladder contracts to expel urine out of the body.

By following this structure, we can create a comprehensive and informative markdown file that summarizes the transcript using clear and concise language.