Excretory System Ch. 15 Sect. 3
Functions of the Excretory System Collects and eliminates wastes from the body and regulates the level of fluid in the body. Controls how much water leaves the body through elimination. The digestive system collects waste products in the intestines. The circulatory system collects waste products in the blood. The body becomes toxic if wastes are not removed.
Types of Excretion The excretory system is made of four body systems. The digestive system collects & removes undigested solids. Urinary system processes, transports, collects, and removes liquid wastes. Respiratory system removes carbon dioxide (CO₂) & water (H₂O). Integumentary system secretes excess salt and water through sweat glands.
Urinary System Organs The urinary system produces, stores and removes liquid waste from the body and help maintain homeostasis. Organs: Kidneys (2), ureters (2), bladder, and the urethra. Those organs work together to process, transport, collect and excrete liquid waste.
Kidneys Kidneys are bean shape Filter (removes) wastes from the blood 2 kidneys (one on each side of body) Red in color due to large volumes of blood Produce hormones that stimulate red blood cell production. Control blood pressure & calcium levels. Contain nephrons (network of capillaries and tubes that filter blood). Urine is produced when blood is filtered.
Kidney Filtration Kidneys filter blood and produce urine in 2 stages: Occurs in the clusters of capillaries in the nephrons. Filter water, sugar, salt and wastes out of blood. Kidneys filter the liquid from the first filtration. Occurs in the small tubes of nephrons. 99% of water & nutrients are reabsorbed into the blood. Remaining liquid and wastes form urine.
Kidney Filtration and Reabsorption Filtration – blood is filtered through the nephrons Reasbsorption – nutrients and some water is reabsorbed by capillaries Secretion – wastes are secreted from the capillaries Excretion – liquids are excreted from the kidney
Ureters, Bladder, and Urethra Urine leaves each kidney through the ureter. Ureters drain into the bladder. Bladder expands and contracts. Urine leaves the bladder through the urethra. The urethra releases the urine outside the body. Urethra contains sphincters (circular muscles). Sphincters control the release of urine.