Kidney Anatomy

Anatomy of kidney

Anatomical position

The kidney is situated inside the abdominal cavity near posterior abdominal wall about 2.5 cm away from the mid line that is vertebral column. The right kidney is slightly lower than the left kidney because of the presence of liver on the right side. It extents from tip of the 9^th costal cartilage upto lower margin of the 3^rd lumber vertebra. This area is called renal fossa. The kidney is a retroperitoneal structure that is its situated behind the peritoneum just above the kidney very important endocrine gland called as adrenal or suprarenal gland.

Size

It is about 4cm X 6cm X 9cm in average adult person.

Shape

It is describe as bean shaped.

Colour

Brown in colour

Weight

250 to 500 gm

Blood Supply

It is supplied by renal artery branched of abdominal aorta.

About 1.5 liter of blood is supped to the kidney per minute. If there is damage to the renal artery in the form of narrowing or blocked due to thromboembolism. The disease of renal artery may cause kidney failure and secondary renal hypertension. The blood comes out by vein which goes to inferior vena cava (IVC)

External covering and relation

The kidney is courted by perinephric fat and renal capsule. The radical border of kidney is concave called as pelvis of kidney. Lateral border is convex, if you divided the kidney into two halves. It is divided into 2 parts, the internal 1/3 is called as medulla and out 2/3^rd is called as cortex.

Microscopic

If we study the section of the kidney under the microscope then we will find that the kidney made up of nephrons. There are 1 million nephrons in each kidney. Nephron is the structural and functional unit of the kidney.

Microscopic structure

Microscopically the nephron has following parts

1.      Clomerulus
2.      Bowman’s Capsule
3.      Proximal convoluted tubule (PCT)
4.      Loop of Henle (LH)
5.      Distal convoluted tubule
6.      Collecting dust/tubule

The renal artery after entering kidney substance divides into millions of capillaries and form network of capillaries inside the kidney substance. All the parts of nephron and the capillaries are single cell layered thick therefore, perfusion and diffusion.

The glomerulus is made up of afferent and effect capillary. The DCT goes up and passes near the glomerulus and Bowman’s capsule and is continuous further as a collecting duct. The part of DCT near glomerulus is having specialized cells called juxtaglomerular apparatus. This part produces a substance called as renin, which is immediately converted into angiotensin I and II which regulates the blood pressure. The collecting duct from different nephron joint to form bigger ducts which produces duct of Bellini this group of ducts of Bellini opens into pyramids. This pyramids open into miner calyx. 3-4 miner calyces joint to produce major calyces. All major calyces opens into pelvis of kidney.

 Function of kidney

1.      Formation of urine
2.      Excretion of waste toxic products like urea, creatinine, etc.
3.      Regulation of water balance.
4.      Regulation of electrolyte balance.
5.      Regulation of pH of the blood.
6.      Regulation of blood pressure.
7.      It helps the process of erythropoiesis by producing substance erythropoietin.

Normal Composition of Urine

Normal adult person the total urine output in 24 hours is 1.5 liter to 3 liter depending upon the fluid intake and the environmental conditions. The urine is mainly composed of following substance.

1.      Water which constituents 90% to 95%.

2.      Urea the remaining solid part contains urea, creatinine, sodium, potassium, chloride, small quantity of hormones.

3.      Bile pigment – Urobilinogen, urobilin which is responsible for pale yellow colour urine some time urine may contain some drugs which the patient has consumed.

When abnormal substances appear in the urine that indicates the presence of some disease. The abnormal substance which may be present in case of diseases are:

1.      Proteins
2.      Glucose
3.      Ketones
4.      Bilirubin
5.      Bile salt
6.      Cells like
7.      Casts
8.      Crystals

Thin layer Chromatography (TLC)

The principle of the Thin Layer Chromatography is the same as described for paper chromatography (partition). Instead of paper the Thin Layer Chromatography of very finely powdered silica gel, alumina, polyacrylamide gel, starch gel or kieselguhr, bound to a glass or plastic plate. Mixture is spread as a thin layer on glass or plastic plates. The chromatographic separation is comparatively rapid in TLC. In case of adsorption thin layer chromatography, adsorbents such as activated silica gel, alumina, kieselguhr are used.

Source : Biochemistry by Dr. U. Satyanarayana

Paper Chromatography

This technique is commonly used for the separation of amino acids, sugars, sugar derivatives and peptides. In paper chromatography, stationary phase is a paper, usually cellulose acetate and the mobile phase is a solvent in which the solute in the mixture are soluble. In this technique, a few drops of solution containing a mixture of the compounds to be separated is applied at one end of the paper (Whatman No. 1 or No. 3 Filter paper), usually above 2 to 3 cm. The paper is dried and dipped into a solvent mixture consisting of butanol, acetic acid and water in 4:1:5 ratio. The aqueous component of the solvent system binds to the paper and forms a stationary phase. The organic component that migrates on the paper is the mobile phase. The filter paper is hung vertically into the solvent, the migration of the solvent is upwards by capillary action is referred to as ascending chromatography. In descending chromatography, the solvents moves downwards. As the solvents flows, it takes along with it the unknown substances. The rate of migration of the molecules depends on the relative solubilities in the stationary phase and mobile phase. 

Remove the paper after a sufficient migration of the solvent, dried and sprayed with a chemical of colour development. Identifies the specific spots at different sites. Ninhydrin, which forms purple complex with ∝-amino acids, is frequently used as a coloring reagent. The chemical nature of the individual spots can be identified by running known standards with the unknown mixture. 

Partition Chromatography

Partition chromatography utilizes differences in the relative solubility of the solute molecules between mobile and the stationary phase. The two phases may be liquid-liquid or gas-liquid. This methodology is used for gas liquid chromatography (GLC) and for high performance liquid chromatography (HPLC). 
It includes 

a.       Paper Chromatography

b.      Thin Layer Chromatography

c.       Gal-Liquid Chromatography

Chromatography

Chromatography is technique discover by Russian Botanist Mikhail Tswett in 1906.
Chromatography is the laboratory technique use for separation of organic and inorganic compounds from the mixture. Includes proteins, peptides, amino acids, lipids, vitamins, carbohydrates, etc. It consists mobile phase and stationary phase.
Types of Chromatography.

1.       Partition Chromatography

a.       Paper Chromatography

b.      Thin Layer Chromatography

c.       Gal-Liquid Chromatography

2.       Adsorption Column Chromatography

3.       Ion Exchange Chromatography

4.       Gel Filtration Chromatography

5.       Affinity Chromatography

6.       High performance liquid chromatography (HPLC)

Immunoelectrophoresis

This technique involves combination of the principles of electrophoresis and immunological reactions (antibodies). Immunoelectrophoresis is useful for the analysis of complex mixtures of antigens and antibodies.
The complex proteins of biological samples are subjected to electrophoresis. the antibody is then applied in a trough parallel to the electrophoretic separation. the antibodies diffuse and when they come in contact with antigens, precipitation occurs, resulting in the formation of precipitin bands which can be identified.
Source : Biochemistry by Dr. U. Satyanarayana

Isoelectric Focussing

This technique is primarily based on the immobilization of the molecules at isoelectric pH during electrophoresis. Stable pH gradients are set up (Usually in a gel) covering the pH range to include the isoelectric points of the components in a mixture. as the electrophoresis occurs, the molecules migrates to positions corresponding to their isolelctric points, get immobilized and form sharp stationary bonds. the gel blocks can be stained and identified. by isoelectric focussing, serum proteins can be separated to as many as 40 bonds. Isoelectric focussing can be conveniently used for the purification of proteins.
Source : Biochemistry by Dr. U. Satyanarayana