Human Body Systems: Lymphatic, Excretory, and Urinary Functions

Lymphatic System: Components and Functions

The lymphatic system is composed of lymph, lymphatic vessels, lymphatic organs, lymphatic tissues, and lymph nodes.

Key Components of the Lymphatic System

Lymph

Lymph is a transparent liquid composed of lymphocytes and interstitial plasma that is formed when blood plasma is filtered as it travels to the tissues.

Lymphatic Vessels

Lymphatic vessels are closed at one end. Lymphatic capillaries are found in tissues, and they join into bigger conduits known as lymphatic veins that eventually connect with blood veins.

Lymphatic Organs and Tissues

Lymphatic organs and tissues perform several functions, such as producing and maturing lymphocytes and purifying blood. The most important lymphatic organs are the spleen and the thymus.

Lymph Nodes

Lymph nodes are made of lymphatic tissue located in specific areas of some lymphatic vessels. They make lymphocytes and release lymph plasma.

The Excretory System: Waste Elimination and Homeostasis

The excretory system is the group of organs and systems that facilitate the elimination of waste products produced by cells after cellular metabolism. The excretory system contributes to the adequate functioning of the body's pH levels. So, it participates in the body's homeostasis.

The Urinary System: Kidneys, Tracts, and Urine Formation

The urinary system is formed by the kidneys and the urinary tracts.

Kidneys

Kidneys are two bean-shaped organs that are located behind the abdomen. Each of them has three parts:

• Renal cortex
• Renal medulla
• Renal pelvis

Nephrons are the structural and functional units of the kidneys.

Urinary Tracts

Urinary tracts are the exit channels for urine that connect the kidneys with the exterior. They include:

• Ureters: Thin tubes that start from each kidney and end in the bladder.
• Urethra: The duct that connects with the exterior. At its end, it has a sphincter that remains closed except for when the nervous reflex occurs.

Urine Formation

Urine is a liquid obtained from the blood, composed of water, minerals, and diverse waste products, mostly urea and uric acid. The process of urine formation has two stages:

1. Glomerular Filtration: It consists of the passage of certain substances from the blood contained in the Malpighian glomerulus to the interior of Bowman's capsule.
2. Tubular Reabsorption: As filtered substances travel through the nephron's tubule, they are reabsorbed, returning to the capillaries that surround them.
   • Reabsorption of water is carried out in the loop of Henle.
   • Other substances are reabsorbed in the distal tubule.