University Biology Report: Urinary System and Fluid Balance Analysis

This biology report provides an overview of the human urinary system, also known as the renal system, including its anatomy and physiological functions. It describes the kidneys, ureters, urinary bladder, and urethra, and their roles in eliminating waste, controlling blood pressure, and maintaining pH and electrolyte balance. The report highlights the importance of understanding anatomy and physiology to comprehend the interconnectedness of bodily systems. Furthermore, it discusses the major factors influencing fluid and electrolyte balance, focusing on the roles of hormones such as aldosterone, angiotensin II, and antidiuretic hormone (ADH). The report examines how these hormones regulate sodium and potassium reabsorption, vasoconstriction, and water reabsorption, respectively, to maintain homeostasis. References are included to support the information presented. This report offers valuable insights into the complex mechanisms of the urinary system and its significance in maintaining overall health.

Running head: BIOLOGY
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Introduction- Anatomy refers to the study of the different body parts and the
relationship between them, which is in contrast to physiology that encompasses exploration
of the function of the body parts. All systems located in the body are interconnected and any
change in one creates mild or devastating effect on another. Hence, the understanding of
anatomy and physiology is imperative to understand the multifaceted nature of the human
body.
Urinary system- It is also referred to as the renal system and comprises of the kidneys,
urethra, ureter, and urinary bladder. The main function of this system is elimination of
nitrogenous waste products from the body, with the aim of controlling blood pressure and
volume, pH, and electrolyte balance. Bean shaped kidneys are present at the back of
abdominal wall and filter the blood that is sent by renal arteries, thus removing unwanted
substances. From the kidneys, the urine moves to the urinary bladder through ureter. Two
ureters located on each side are thin and long tubes comprising of smooth muscles and they
push the urine downwards. The urinary bladder acts as a temporary reservoir and contains
detrusor muscle and different folds called rugae. The urethra acts as the passage of urine
outside the human body (Rehfeld, Nylander & Karnov, 2017). The mouth of the urethra is
guarded by sphincter muscles which when relaxed, help in urine expulsion or micturition.
The chief functions of the urinary system are to control blood composition and volume,
regulate blood pressure, maintain homeostasis of blood, help in red blood cell production,
facilitate synthesis of calcitrol (vitamin D active form), and storage of uric acid and urea.
Major factors influencing fluid and electrolyte balance- Reabsorption of sodium
occurs from the renal filtrate, in addition to the excretion of potassium to the filtrate that is
present in the renal collecting tubule. Two hormones play an important role in maintaining
the level of electrolytes namely, aldosterone and angiotensin II. Aldosterone increases
potassium excretion and sodium reabsorption in distal tubule. Increase in potassium or

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decrease in sodium triggers release of aldosterone that helps in conserving water and
increasing its level in plasma by lowering sodium excretion. Angiotensin II results in
vasoconstriction that brings about an increase in the systemic blood pressure, thereby
increasing glomerular filtration and signaling aldosterone release from adrenal cortex
(Ishizawa et al., 2019). ADH or antidiuretic hormone, also referred to as vasopressin
regulates the water that is reabsorbed from collecting tubules and ducts. On detecting increase
in blood plasma concentration, ADH release is triggered by the hypothalamus from the
posterior pituitary that causes constriction of the arterioles in peripheral circulation, thus
lowering blood flow to extremities, and subsequent increase in blood supply to other body
parts (Watson & Austin, 2018). The hormone also triggers movement of epithelial cells lining
the collecting tubules, thus increasing water permeability and causing more water
reabsorption in the circulating bloodstream. Decrease in concentration of blood plasma and
ADH leads to removal of aquaporin, thus reducing water passage to urine and bloodstream
(Rundgren & Svensen, 2018).
Conclusion- To conclude, human anatomy and physiology provide assistance in
gaining a sound understanding of the ways by which different organs in the body work, and
also provide in-depth explanation for the mechanism of homeostasis maintenance.

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References
Ishizawa, K., Wang, Q., Li, J., Yamazaki, O., Tamura, Y., Fujigaki, Y., ... & Shibata, S.
(2019). Calcineurin dephosphorylates Kelch-like 3, reversing phosphorylation by
angiotensin II and regulating renal electrolyte handling. Proceedings of the National
Academy of Sciences, 116(8), 3155-3160.
Rehfeld, A., Nylander, M., & Karnov, K. (2017). The Urinary System. In Compendium of
Histology (pp. 495-515). Springer, Cham.
Rundgren, M., & Svensen, C. H. (2018). Fluid balance, regulatory mechanisms, and
electrolytes. Fluid Therapy for the Surgical Patient, 1, 15-44.
Watson, F., & Austin, P. (2018). Physiology of human fluid balance. Anaesthesia & Intensive
Care Medicine.