Circulatory and Excretory Systems: Functions and Anatomy
What is the Circulatory System?
The circulatory system is responsible for carrying the products of digestion and oxygen obtained through the respiratory system to all the cells of the body. It also collects waste products and takes them to the excretory system where they will be eliminated.
What Organs Form the Circulatory System?
It is formed by a central body called the heart and blood vessels (arteries, veins, and capillaries).
How is the Heart Shaped?
The heart is a hollow organ composed of muscle tissue called the myocardium. It is located in the rib cage between the lungs, deployed slightly to the left side of the body. Inside, there are four chambers: the atria and the ventricles.
How are Arteries, Veins, and Capillaries Composed?
- Arteries are formed by strong, elastic, muscular walls that contract and relax, driving blood.
- Veins are not very elastic, but many have valves that prevent the backflow of blood.
- Capillaries are very thin and have a single layer of cells.
What is the Cardiac Cycle and What Movements Occur in it?
The cardiac cycle is the term that comprises the sequence of events related to the flow of blood that must occur from the beginning of one heartbeat to the beginning of the next. Each beat includes three stages: atrial systole, ventricular systole, and diastole.
How is Blood Formed?
Blood is composed of liquid plasma and solids. The plasma is a liquid that has proteins and is responsible for carrying nutrients and waste. There are three types of blood cells:
- White blood cells: defend the cell against infections.
- Platelets: are involved in the process of coagulation.
- Red blood cells: are composed of hemoglobin, which gives blood its red color and is responsible for carrying oxygen throughout the blood.
Excretion: What is it?
Excretion plays a vital role in the elimination of waste products from the processes carried out inside the cell. If these waste products were to accumulate in our body, they would quickly lead to death due to their high toxicity.
What Organs Act in the Excretion of Toxic Substances?
The organs that act are the kidneys, large intestine, lungs, sweat glands, and urinary system.
What Organs Make up the Urinary System?
The kidneys are located at the waist and are formed by a million microscopic units called nephrons. From the kidneys, two tubes called ureters carry the urine formed in the kidneys to the bladder. The bladder is an elastic muscular organ that stretches as it fills with urine. The tube that connects the bladder to the exterior and produces the discharge or micturition is called the urethra.
What is the Microscopic Unit Forming Nephrons?
The microscopic units that form the kidneys are the nephrons. Each glomerulus has a surrounding nephron called Bowman’s capsule, followed by the kidney, which flows into the collecting duct.
How is Urine Formed and What Steps Does it Meet?
The formation of urine is accomplished through three processes:
- Filtration: The blood plasma passes through the glomerulus, which functions as a sieve, letting through water and small substances to the Bowman’s capsule while retaining the larger substances that are useful for the body, such as blood cells, platelets, proteins, and lipids.
- Reabsorption: Occurs in the kidney where small substances that were filtered, such as glucose, vitamins, and salts, are recovered. Also, 95% of the filtered water is recovered.
- Excretion: The passage of urine into the bladder for disposal.
How Much Urine is Produced and What is the Bladder’s Capacity?
Between 1 and 1.5 liters of urine are produced. The capacity of the bladder is 300 to 350 cm3.