Bowman's capsule (or the Bowman capsule, capsula glomeruli, or glomerular capsule) is a cup-like sac at the beginning of the tubular component of a nephron in the mammalian kidney that performs the first step in the filtration of blood to form urine. A glomerulus is enclosed in the sac. Fluids from blood in the glomerulus are collected in the Bowman's capsule (i.e., glomerular filtrate) and further processed along the nephron to form urine. This process is known as ultrafiltration.
The main function of Bowman’s capsule and glomerulus is carrying out the process of ultrafiltration.
The process of filtration of the blood in the Bowman's capsule is ultrafiltration (or glomerular filtration), and the normal rate of filtration is 125 ml/min, equivalent to 80 times the daily blood volume.

Any proteins under roughly 30 kilodaltons can pass freely through the membrane, although there is some extra hindrance for negatively charged molecules due to the negative charge of the basement membrane and the podocytes.

Any small molecules such as water, glucose, salt (NaCl), amino acids, and urea pass freely into Bowman's space, but cells, platelets and large proteins do not. As a result, the filtrate leaving the Bowman’s capsule is very similar to blood plasma, (filtrate or glomerular filtrate is composed blood plasma minus plasma protein i.e. it contains all the components of blood plasma expect the proteins)in composition as it passes into the proximal convoluted tubule.

In the kidney, a tubular structure called the nephron filters blood to form urine. At the beginning of the nephron, the renal glomerulus is a network (tuft) of capillaries that performs the first step of filtering blood.The glomerulus is surrounded by Bowman's capsule. The blood plasma is filtered through the capillaries of the glomerulus into the Bowman's capsule.The glomerulus is surrounded by Bowman's capsule. The blood plasma is filtered through the capillaries of the glomerulus into the Bowman's capsule. The Bowman's capsule empties the filtrate into a tubule that is also part of the nephron.

A glomerulus receives its blood supply from an afferent arteriole of the renal circulation. Unlike most other capillary beds, the glomerulus drains into an efferent arteriole rather than a venule. The resistance of these arterioles results in high pressure within the glomerulus, aiding the process of ultrafiltration, where fluids and soluble materials in the blood are forced out of the capillaries and into Bowman's capsule.
With reference to excretion serum is serum albumin. Serum albumin is produced by the liver, occurs dissolved in blood plasma and is the most abundant blood protein in mammals. Albumin is essential for maintaining the oncotic (colloid osmotic pressure) pressure needed for proper distribution of body fluids between blood vessels and body tissues; without albumin, the high pressure in the blood vessels would force more fluids out into the tissues. Albumin functions primarily as a carrier protein for steroids, fatty acids, and thyroid hormones in the blood and plays a major role in stabilizing extracellular fluid volume by contributing to oncotic pressure (known also as colloid osmotic pressure) of plasma.