Excretion in humans and plants | Life processes | Class 10 Biology | Khan Academy

Summary

This video explains the excretion process in humans and plants. In humans, the kidneys filter blood to form urine, which is transported to the bladder via the ureter before being expelled. The nephron plays a key role in filtration and reabsorption of useful substances. In plants, excretion is simpler. Waste gases like oxygen and carbon dioxide are released through the stomata, while other waste products are stored in vacuoles, bark, or leaves, which are shed when full. Some waste can also be excreted through the soil.

Takeaways

• 💧 In humans, the kidneys form urine, which travels through the ureter into the bladder where it is stored before being excreted.
• 🩸 Blood enters the kidneys through the renal artery, where it is filtered to remove unwanted substances, forming urine.
• 🔄 Oxygen is used by kidney cells, and the filtered, deoxygenated blood exits through the renal vein, returning to the heart.
• 🧪 Urine travels from the kidneys through the ureter into the bladder, where it stays until it's excreted.
• 🔍 Filtration in the kidney happens at the nephron, specifically in the glomerulus and Bowman's capsule.
• 🧪 The first filtration stage happens in the glomerulus, where a mixture of unwanted and wanted substances is filtered out.
• 💧 The nephron reabsorbs important substances like water, salts, and glucose, ensuring they return to the blood.
• 🚰 The remaining unwanted materials form urine, which is eventually excreted from the body.
• 🌿 In plants, excretion occurs through simpler processes like releasing gases through the stomata and storing waste in vacuoles.
• 🍃 Plants can also excrete waste by shedding leaves or bark, and by releasing waste products into the soil.

Q & A

What are the main parts of the excretory system in humans?

The main parts of the excretory system in humans are the kidneys, ureter, bladder, and urethra. The kidneys form urine, which is passed down through the ureter to the bladder, where it is stored until excretion.

How does blood reach the kidneys, and what happens to it there?

Blood reaches the kidneys through the renal artery. Inside the kidney, the blood gets filtered, removing waste products to form urine. The deoxygenated and filtered blood then leaves through the renal vein and returns to the heart.

What is the role of the nephron in the kidney?

The nephron is the functional unit of the kidney responsible for filtering blood. It has two stages of filtration: the first happens in the glomerulus inside the Bowman's capsule, and the second involves reabsorption of necessary substances like water and salts as the filtered fluid passes through the nephron.

What happens during the first stage of filtration in the nephron?

In the first stage, blood enters the glomerulus, where due to pressure, various substances, including waste products like urea and some useful substances such as glucose, salts, and water, pass into the Bowman's capsule, starting the filtration process.

Why is reabsorption necessary in the nephron, and where does it occur?

Reabsorption is necessary because during filtration, some useful substances like water, salts, and glucose are filtered out with waste. Reabsorption occurs as the filtered fluid passes through the nephron, ensuring that the body retains essential substances.

How does urine exit the body after being formed in the kidney?

After urine is formed in the kidney, it passes through the ureter to the bladder, where it is stored until it is expelled from the body through the urethra.

How do plants excrete waste products?

Plants excrete waste products mainly through the stomata in the form of gases like oxygen and carbon dioxide. They also store waste products in vacuoles within their cells or transport them to bark or leaves, which can be shed to remove waste.

What role do vacuoles play in plant excretion?

Vacuoles in plant cells serve as storage for waste products. If the vacuoles become full, waste can be transported to other parts of the plant, such as bark or leaves, which can be shed to dispose of the waste.

What happens to waste products in plants if vacuoles are full?

If vacuoles are full, plants can transport waste to other parts, such as bark or leaves, which will eventually be shed, allowing the plant to eliminate waste. Some waste may also be excreted into the soil.

What is the significance of the glomerulus and Bowman's capsule in the nephron?

The glomerulus and Bowman's capsule are critical in the first stage of filtration. The glomerulus, a capillary network, allows substances to pass into the Bowman's capsule due to pressure, initiating the filtration process within the nephron.