Structure and function of kidneys, nephron, ureters, urinary bladder and urethra

Structure and function of kidneys, nephron, ureters, urinary bladder and urethra

Structure and Function of Kidneys

• Kidneys are two bean-shaped organs located on either side of the spine, just below the rib cage. They are roughly the size of a fist.
• Each kidney is made up of about a million filtering units known as nephrons.
• The kidneys are responsible for filtering waste products, excess nutrients, and liquids out of the bloodstream to form urine.

Structure and Function of Nephrons

• Nephrons are the functional units of the kidneys, each comprising a glomerulus and a tubule.
• The glomerulus is a tiny blood vessel or capillary that performs the first step of filtering blood, while the tubule returns needed substances to the blood and pulls out additional wastes.
• All the nephrons work together to remove toxic wastes and excess substances through ultrafiltration, reabsorption, and secretion.

Structure and Function of Ureters

• Ureters are thin, muscular tubes that extend downward from the kidneys to the bladder.
• They act as conduits for urine, using peristaltic waves (muscle contractions) to force urine down into the bladder.

Structure and Function of the Urinary Bladder

• The bladder is a balloon-like organ located in the pelvic cavity.
• It essentially functions as a temporary storage for urine (capacity of up to 500 ml), which then facilitates its later expulsion from the body through the urethra.
• It features a muscular wall that allows it to expand as it fills with urine and contract when it is time to urinate.

Structure and Function of the Urethra

• The urethra is a tube that carries urine from the bladder to the outside of the body.
• In males, it has a dual function, also carrying sperm and seminal fluid during ejaculation.
• Both sexes have sphincter muscles at the bladder-urethra junction which ensure urine is retained until the bladder is purposely emptied.