Main Difference – Bowman’s Capsule vs Glomerulus
A nephron is the microscopic functional unit of the kidney, which filters blood to produce urine. Kidney removes excess water and the nitrogenous wastes from the body of animals. Renal corpuscle and renal tubule are the two components of the nephron. Bowman’s capsule and glomerulus are the two structural components of the renal corpuscle. Renal corpuscle is located in the renal cortex. The major function of the renal corpuscle is to filter blood plasma. The main difference between Bowman’s capsule and glomerulus is that Bowman’s capsule is a single layer of epithelial cells surrounding the glomerulus whereas glomerulus is a cluster of blood capillaries filtering the blood plasma.
Key Areas Covered
1. What is Bowman’s Capsule
– Definition, Structure, Function
2. What is Glomerulus
– Definition, Structure, Function
3. What are the Similarities Between Bowman’s Capsule and Glomerulus
– Outline of Common Features
4. What is the Difference Between Bowman’s Capsule and Glomerulus
– Comparison of Key Differences
Key Terms: Blood, Bowman’s Capsule, Glomerulus, Kidney, Nephron, Renal Corpuscle, Renal Tubule
What is Bowman’s Capsule
Bowman’s capsule refers to a membranous, double-walled capsule, which surrounds the glomerulus of the nephron. It is a part of the renal corpuscle. Renal corpuscle is the initial structural component of a nephron, which is involved in the filtration of blood plasma. Bowman’s capsule is continuous with the proximal convoluted tubule of the renal tubule, the latter part of the nephron. Bowman’s capsule encircles a cluster of blood capillaries called the glomerulus. The structure of the renal corpuscle is shown in figure 1.
Figure 1: Renal Corpuscle
Bowman’s capsule is made up of two layers of epithelial cells. The glomerulus is encircled by the inner layer of the Bowman’s capsule. The blood plasma which is filtered by the glomerulus is sent to the space between the double-membrane structure of the Bowman’s capsule. The outer layer of the Bowman’s capsule is continuous with the renal tubule.
What is Glomerulus
Glomerulus refers to a cluster of small blood capillaries in the nephron, which filters the blood plasma. It is the other part of the renal corpuscle and is encircled by the Bowman’s capsule. The blood capillaries of the glomerulus are made up of a single epithelial cell layer. The two types of cells associated with the epithelial cells of the glomerulus are podocytes and mesangial cells. Podocytes wrap around the blood capillaries by their pedicles, acting as a filtration barrier. The gaps between the pedicles serve as thin filtration slits. The passage of large molecules from the slits is restricted by various proteins associated with the slits such as nephrin, P-cadherin, and podocalyxin. Red blood cells, white blood cells, platelets, serum albumin, and gamma globulin like blood components remain in the capillaries of the glomerulus, while small molecules such as glucose, amino acids, electrolytes, and nitrogenous wastes are filtered into the space of the Bowman’s capsule. Glomerulus receives blood through the afferent arteriole, which is a branch of the renal vein. On the other hand, filtered blood is taken away from the glomerulus through the efferent arteriole, which is a branch of the renal artery. Podocyte structure in the glomerulus is shown in figure 2.
Figure 2: Podocytes in the Glomerulus
Mesangial cells can be either extraglomerular or intraglomerular. The extraglomerular mesangial cells are found between the afferent arteriole and efferent arteriole while intraglomerular mesangial cells are found between the blood capillaries of the glomerulus. Both types of mesangial cells remove trapped residues such as protein clusters, keeping the filtrate free of debris.
Similarities Between Bowman’s Capsule and Glomerulus
- Bowman’s capsule and glomerulus are the two components of the renal corpuscle.
- Both Bowman’s capsule and glomerulus are the initial structural components of a nephron.
- Both Bowman’s capsule and glomerulus are made up of a single, epithelial cell layer.
- Both Bowman’s capsule and glomerulus are involved in the filtration of blood.
Difference Between Bowman’s Capsule and Glomerulus
Definition
Bowman’s Capsule: Bowman’s capsule refers to a membranous, double-walled capsule, which surrounds a glomerulus of the nephron.
Glomerulus: Glomerulus refers to a cluster of small blood capillaries in the nephron, which filters blood plasma.
Significance
Bowman’s Capsule: Bowman’s capsule is a cup-like structure.
Glomerulus: Glomerulus is a cluster of blood capillaries.
Structure
Bowman’s Capsule: Bowman’s capsule consists of two epithelial cell layers.
Glomerulus: Glomerulus consists of a single epithelial layer, which is surrounded by podocytes and mesangial cells.
Function
Bowman’s Capsule: Bowman’s capsule receives the filtrate of the glomerulus.
Glomerulus: Glomerulus filters the blood plasma.
Blood Cells and Platelets
Bowman’s Capsule: Bowman’s capsule does not receive blood cells and platelets.
Glomerulus: Glomerulus contain blood cells and platelets.
Conclusion
Bowman’s capsule and glomerulus are the two components of the renal corpuscle, which is the initial part of the nephron. Both Bowman’s capsule and glomerulus are made up of a simple squamous epithelium. Glomerulus consists of blood capillaries, which filter the blood plasma. Bowman’s capsule encircles the glomerulus, receiving the filtrate of the glomerulus. It is continuous with the proximal convoluted tubule of the nephron. The main difference between Bowman’s capsule and glomerulus is their structure and function.
Reference:
1.“ Bowman’s Capsule.” InnerBody, Available here.
2.“Glomerulus.” LifeMap Discovery®, Available here.
Image Courtesy:
1. “Juxtaglomerular Apparatus and Glomerulus” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
2. “2613 Podocytes” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
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