• Human anatomy


    Except for urinary bladder which is endodermal in origin, the whole excretory system is Except urinary bladder which is endodermal in origin, the whole excretory system is Except mesodermal. In human the kidney is retroperitoneal i.e., the kidney is located outside the coelomic cavity and is covered by peritoneum (coelomic epithelium) from the ventral side only. The size of each kidney is ~10 cm and it weighs is ~150 g. The two kidneys are asymmetrical, the Rt. being posterior to the Lt. Each kidney is bean-shaped with a groove (hilus) in the middle. The hilus is absent in frog’s kidney. The white fibrous connective tissue-covering around kidney is called renal…

  • Countercurrent-in-the-kidney.jpg
    Human anatomy

    Urine Formation

    3−steps are involved in the formation of urine A) Ultra filtration It is filtration under pressure. Glomerular capillary pressure (45 mm of Hg) favours filtration. The Colloidal osmotic pressure (due to plasma proteins, particularly albumin) acts against filteration. Its value is ~20 mm of Hg. The Capsular filtrate pressure, due to the glomerular filtrate in the Bowman’s capsule, also acts against filtration. Its value is ~10 mm of Hg. Net filtration pressure = 45 − (20+10) mm of Hg = 15 mm of Hg or 10 − 20 mm of Hg. Only 1/5 of plasma (20%) gets filtered from glomerulus per unit time. It is about 125 ml per minute.…

  • Biochemistry

    Q & A on Cell Structure

    Q1: Which one of the following cell structures can be seen with a light microscope? (Mark 1) A. mitochondrion B. ribosome C. rough ER D. smooth ER Ans: (A) Mitochondrion Q2: The use of electrons as a source of radiation in the electron microscope allows high resolution to be achieved because electrons: (Mark 1) A. are negatively charged. B. can be focused using electromagnets. C have a very short wavelength. D travel at the speed of light. Ans: (C) have a very short wavelength. Q3: Which one of the following structures is found in animal cells, but not in plant cells? (Mark 1) A. cell surface membrane B. centriole C.…

  • Human anatomy

    An Overview On Pineal Gland

    The pineal gland is a small, pea-shaped gland in the brain. Its function isn’t fully understood. Researchers do know that it produces and regulates some hormones, including melatonin. It is ectodermal in origin. It is unpaired (Single) and is attached to epithalamus of the diencephalon. It is, therefore, also known as Epiphysis cerebri (Pituitary, attached to the hypothalamus, is called Hypophysis cerebri) It is considered to be the ‘seat of soul’. In a human, it starts degenerating at the age of 7-8 years. The calcium and magnesium salts are deposited in this gland at later stages and the structure is then known as ‘brain sand’. This gland produces single hormone…

  • Human anatomy

    An overview of Pituitary Gland

    It is called master gland (master of endocrine orchestra) as it regulates the functioning of other endocrine glands like thyroid, Adrenal cortex, testes and ovaries etc. However, the secretions of pancreas, thymus and pineal body are not regulated by the hormones of the pituitary. Pituitary is a single or unpaired gland weighing about 0.5 gm. It is present in the ‘Sella tursica’ cavity of Basi-sphenoid bone and is attached to the floor of Diencephalon (hypothalamus) of forebrain through a stalk called Infundibulum. As it is present below diencephalon of fore-brain it is also known as Hypophysis cerebri. In mammals, it is ectodermal in origin. It consists of two-parts – (1)…

  • Biochemistry

    What is Prion?

    Prion, an abnormal form of a normally harmless protein found in the brain that is responsible for a variety of fatal neurodegenerative diseases of animals, including humans, called transmissible spongiform encephalopathies. In the early 1980s American neurologist, Stanley B. Prusiner and colleagues identified the “proteinaceous infectious particle,” a name that was shortened to “prion” (pronounced “pree-on”). Prions can enter the brain through infection, or they can arise from mutations in the gene that encodes the protein. Once present in the brain prions multiplies by inducing benign proteins to refold into the abnormal shape. This mechanism is not fully understood, but another protein normally found in the body may also be…

  • Microbiology

    Morphology of Bacteria

    Size The unit of measurement used in bacteriology is the micron (micrometre) 1 micron (μ) or micrometre (μm) – one-thousandth of a millimetre 1 millimicron (mμ) or nanometer (nm) – one-thousandth of a micron or one-millionth of a millimetre 1 Angstrom unit (Å) – one-tenth of a nanometer The limit of resolution with the unaided eye is about 200 microns. Bacteria aresmaller which can be visualized only under magnification. Bacteria come in a great many sizes and several shapes. Most bacteria range from 0.2 to 2.0 μm in diameter and from 2 to 8 μm in length. (anoverall average size of 1 to 10 μm.) Shape Depending on their shape,…

  • Human alimentary tract
    Biology,  Human anatomy

    Human Digestive Enzymes

    Human digestive enzymes are mainly synthesized in the salivary glands and in the pancreas As we’ve discussed, enzymes are made up of amino acids found in proteins so a ready supply of these building blocks is required to ensure there are optimal levels of digestive enzymes at all times. Digestive enzymes are mixed in the saliva and pancreatic juices and are released into the mouth and small intestines, respectively, to support digestion of proteins, fats, and carbohydrates. Their synthesis and release occur via carefully orchestrated and tightly controlled hormone systems that are activated not just when food hits our taste buds but also by the sight, smell and sound of…

  • Q & A

    Q & A on Cell Structure

    Q: What is cell theory? Cell theory asserts that the cell is the constituent unit of living beings. Before the discovery of the cell, it was not recognized that living beings were made of building blocks like cells. The cell theory is one of the basic theories of Biology. Q:  Are there living beings without cells? Viruses are considered the only living beings that do not have cells. Viruses are constituted by genetic material (DNA or RNA) enwrapped by a protein capsule. They do not have membranes and cell organelles nor do they have self-metabolism. Q:  In 1665 Robert Hooke, an English scientist, published his book Micrographia, in which he…

  • A level biology

    What is the function of Golgi body?

    The Golgi body is actually a pile or stack of membranous structures called cisternae. The numbers of cisternae in a single stack vary between 6-8. In some protists, however, the number could extend up to 60. The Golgi bodies are found in both plant & animal cells. The cisternae of Golgi body have four structural components i.e., cis-Golgi, endo-Golgi, medial-Golgi and trans-Golgi. The vesicles extending from endoplasmic reticulum fuse with the network. These vesicles then enter the stacks of Golgi body and finally reach the trans-Golgi. The different regions of Golgi apparatus contain different types of enzymes. These enzymes have certain specific tasks assigned to them. Vesicles leave the Golgi…


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