2.75) Urine

Recall that urine contains water, urea and salts

Urine contains salts, water and urea.

Water and salt particularly affects the composition of the tissue fluid. This is called osmoregulation.

The removal of urea is part of the process of excretion of metabolic waste.

The composition of urine varies depending on the condition of each person, both externally and internally. 

2.74) ADH

Describe the role of ADH in regulating the water content of the blood

ADH = anti-divretic hormone

produced at the region of the brain called hypothalamus 

Like all hormones, it flows through the blood stream, and its target is the kidney

The effect of ADH is to control the water composition in blood. It has the ability to make the blood more or less concentrated. Tissue fluid is isotonic. 

ADH actually targets the collecting duct. It allows more water to come out of the collecting duct.

Recall that water is selectively reabsorbed into the blood at collecting duct. 

It is possible to absorb even more water back into the blood with the help of ADH. ADH creates more pores on the collecting duct, so more water can escape into the blood.

The consequence of ADH secretion is that the urine will be more concentrated and will have a lower volume. 

Extension: How does our brain respond with ADH on the hot day? Cold Day? When we're dehydrated?

2.73) Glucose Reabsorption

Understand that selective reabsorption of glucose occurs at the proximal convoluted tubule

Glucose from glomerula filtrate --> back into blood vessel

Ultrafiltration occurred in the Bowman's capsule. 

Water is selected back into blood stream at collecting duct, and thus urine is passed down into the pelvic region.

Normally, urine does not contain glucose. If there glucose is present in urine, it would be a condition called diabetes. 

In the first convoluted tubules (proximal convoluted tubule) section, glucose is removed and is taken back into the blood vessel. 

2.72) Water re-absorption

Understand that water is reabsorbed into the blood form the collecting duct

The blood went through ultrafiltration under high pressure in Bowman's capsule, and gumerula filtrate, which contains glucose, water, salts and urea, is formed. 

However, when filtration occurred, it will filter out too much water. As the filtrate passes along the tubules and reaches the collecting duct and passes through it, water is removed from the filtrate and is returned back into blood vessel. Water has been selected and is reabsorbed into the blood. We call the process selected reabsorption of water, and it occurs in the collecting duct. 

2.71) Ultrafiltration

Describe ultrafiltration in the Bowman's capsule and the composition of the glomerular filtrate

Nephron carries out the filtration of our blood, which will result into filtered blood and urine.

Urine is composed largely of water, salts (Sodium chloride, etc.) and urea (which contains toxic nitrogen waste of the body). 

The first process started at Bowman's capsule...

Bowman's capsule - where the filtration process begins, known as ultrafiltration of molecules. 

Blood arrives in the kidney through the blood vessel called afferent arteriole where the blood is under high pressure. Blood vessels then started to brand and became very much slower into twisted parts called glomerulus. The blood then comes out through the blood vessel efferent arteriole in which the diameter of this vessel is smaller and more narrow than the afferent arteriole's. The consequence of narrowed vessels is the increase of blood pressure. In other words, the blood pressure increases in the glomerulus. 

Moreover, this forces the liquid within blood called plasma which contains all the components dissolved in blood, for instance, water (solvent), salts, amino acid, glucose, and urea, out of the blood vessel and into the inner space of Bowman's capsule. When the plasma is forced into the Bowman's capsule we called it glomerula filtrate. 

To conclude, the blood has been filtered through undergoing high pressure due to the narrowing glomerulus, which forces in plasma out from the blood (in the Bowman's capsule.) 

2.70) Nephron Structure

Describe the structure of a nephron, to include Bowman's capsule and glomerulus, convoluted tubules, loop of Henle and collecting duct.

Nephron - functional unit of the kidney which does the filtration and composition of blood.

The renal artery is a branch of aorta that takes blood into the kidney. 

The kidney then filters the blood and the content which are removed are called urine which goes down the structure called ureter to be collected in to bladder.

The filtered blood exits in the blood vessel called renal vein and is returned to the vena cava.

If we slice the kidney open, we can see...

The outer region of the kidney is called the cortex (lighter color.)

The middle region is called medulla (with slightly darker color).

The innermost layer is a space called the pelvic region (slightly colored), which is where the urine collects and is drained down the ureter. 

The difference in color is because kidney is made of millions of different tubes. 

The tube starts on the edge of the medulla and grows through the medulla directly outward to the cortex. As it travels up the cortex, it whines back in and out of the medulla, until it reaches a dead end. The deadened structure is called Bowman's capsule.

The tubular structure is called the nephron

(according to the diagram below)

Above the dotted line is the cortex region, and below is the medulla region. 

At the end of the tube is will grows into the pelvic region where and is where urine emerges. 

The tube is made up of twisted section called convoluted tubules and the tube which connects the convoluted tubules into the pelvic region is called the collective duct. 

The part the dips back into the medulla is called the Loop of Henle

The Bowman's capsule is the dead end structure in which contains tight knot blood vessels called glomerulus.

The first twisted section is known as the proximal convoluted tubules (PCT).

The second twisted section is know as the Distal convoluted tubules (DCT).

It is the arrangement of the nephron which gives us the difference in color between regions in the kidney. There are millions of nephron in a single kidney.