Yogy's biology

02 Reproduction in Lower and Higher Animals - part 17 - Infertility Infertility :  Infertility is defined as the  inability to conceive naturally after (one year of) regular unprotected intercourse.  The causes of infertility could be physical, congenital, diseases, immunological or even psychological.  The common physical causes in  females  are -   polycystic ovary syndrome (PCOS) hormonal imbalance endometriosis  while in  male , it is - less sperm count and  small size of penis.  prior to 1978, infertile couple had two options,  adopt or be childless.  Today infertile couples have many options to have a child such as -  fertility drugs test tube babies artificial insemination IUI surrogate motherhood, etc.   The couple could be assisted to have child / children through certain special techniques commonly known as Assisted Reproductive Technologies (ART). IVF (In Vitro Fertization) :  It is a process...

02 Reproduction in Lower and Higher Animals - part 16 - Sexually Transmitted Diseases Sexually Transmitted Diseases (STDs) :  Diseases or infections which are transmitted through sexual intercourse are collectively called Sexually Transmitted Diseases (STDs) or  Venereal Diseases (VDs) or Reproductive Tract Infections (RTI).  The major venereal diseases are  syphilis and gonorrhoea. Sexually Transmitted Diseases (STDs) : 1.  Name of Disease   :  Syphilis Causative agent   :  Treponema pallidum  (Bacteria) Incubation period  :   3-4 weeks  Infection site   :   Mucous membrane in genital, rectal and oral region.  Symptoms   : Primary lesion called  chancre at the site of infection.  Chancre is formed on external genitalia, skin rashes and mild fever, inflamed joints, loss of hair.  Paralysis, Degenerative changes occur in the heart and brain.  Preventive measures : ...

02 Reproduction in Lower and Higher Animals - part 14 - Reproductive Health Reproductive Health:  According to  World Health Organisation (WHO ), reproductive health means total wellbeing in all aspects of reproduction- its emotional, behavioural and social aspects along with the physical ones.  Therefore, a society with people having physically and functionally normal reproductive organs and normal emotional and behavioural interactions amongst them in all sex-related aspects might be called  reproductively healthy society .  Of all the social goals of India, an important one is to  attain total reproductive health .  India was amongst the first few countries in the world to initiate action plans and programmes at a national level to improve reproductive health.  All these improved programmes cover wider areas related to reproduction.  These programs are currently in operation under the Reproductive and Child Health Care (RCH) programmes. Go...

02 Reproduction in Lower and Higher Animals - part 13 - Parturition and Lactation Parturition:  Humans are  viviparous , as they give birth to their young ones.  Parturition is the process of giving birth to a baby.  The physical activities involved in parturition like uterine and abdominal contractions, dilation of cervix and passage of baby are collectively called  labour .  Labour is accompanied by localised sensation of discomfort or agony called  labour pains.   Parturition is controlled by a  complex neuroendocrine mechanism . Signals arise from the fully formed foetus and placenta cause mild uterine contractions.  It is acompanied by rise in  estrogen- progesterone ratio , increase in  oxytocin  receptors in uterine muscles. They cause  vigorous contractions of myometrium  of uterus at the end of pregnancy.  The fully developed foetus gives signals for the uterine contractions by secreting  Adren...

02 Reproduction in Lower and Higher Animals - part 12 - Placenta Placenta:  It is a  flattened, discoidal organ  in the uterus of a pregnant woman.  The placenta is a  temporary structural and functional connection  between foetal and maternal circulation.  The placenta facilitate the  supply  of  oxygen and nutrients  and also for  removal  of  carbon dioxide and excretory wastes  produced by the foetus.  The placenta is attached to the wall of the uterus and to the  baby's umbilical cord .  Placenta is the only organ, which is formed of tissues from two different individuals- the mother and the foetus.  Part of the placenta contributed by the foetus is called the  foetal placenta  and it is the  chorionic villi .  The other part which is rich in blood supply shared by the mother. It is a part of uterine wall, termed as  maternal placenta.   So human placenta is ...

02 Reproduction in Lower and Higher Animals - part 11 - Pregnancy Pregnancy :  It is the condition of carrying one or more embryos in the uterus. It is also called  gestation .  It refers to the period between fertilization of the egg, upto parturition.  The average period of pregnancy in human lasts for  266 days  from fertilization or 280 days (266+14) counted from  LMC- Last Mensturation Cycle.  This pregnancy peroid of approximately nine months is divided into  three trimesters  of three months each. First Trimester ( from fertilization to 12th week) : It is the time of  most radical changes  in mother and embryo.  The embryo receives nutrients in the first 2-4 weeks directly from the  endomerium .  It is the main period of  organogenesis  and the development of body organs.  By the end of eight weeks, the major structures found in the adult are formed in the embryo in a  rudimentary ...

02 Reproduction in Lower and Higher Animals - part 10 - Fate of germinal layers Fate of germinal layers:  Ectoderm : Ectoderm gives rise to epidermis  of skin, hair, nails, sweat glands,  salivary glands, mammary glands,  lacrimal glands, sebaceous glands,  cornea, lens, retina, conjunctiva,  nasal epithelium, enamel of teeth, internal and external ear, foregut, hindgut, adrenal medulla, anterior and posterior pituitary, pineal  gland, entire nervous system.  Mesoderm  :  Mesoderm forms all types of muscles (except iris muscles ciliary muscles of eye which originate from ectoderm), connective tissues, dermis of skin, adrenal cortex, heart,blood, blood vessels, lymphatic vessels, middle ear, dentine of  teeth, urinary and reproductive ducts, gonads, kidneys, sclera and choroid of eye. Endoderm :  Endoderm devlops into epithelium of mid- gut, glands of   stomach and intestine, tongue,  tonsils, lungs, trachea, bron...

02 Reproduction in Lower and Higher Animals - part 09 - Embryonic development Embryonic development :  The zygote formed as a result of  syngamy  is activated to divide.  Cleavage  : It is the process of early mitotic division of the zygote into a hollow multicellular  blastula .  It does not involve the growth of the daughter cells. The cells formed by cleavage are called  blastomeres .  Since, there is no growth phase between the cleavages, the size of blastomeres will be reduced with every successive cleavage.  As the size reduces, the metabolic rate increases.  Subsequent cleavages are thus faster than earlier one.  This requires  rapid replication of DNA and high consumption of oxygen.  Process of cleavage :  In human, cleavage is  holoblastic  i.e. the whole zygote gets divided.  The cleavage planes may be longitudinal or meridional and equatorial or horizontal.  It is radial and indeter...