CLEAVAGE

 The human egg is alecithal because it is contain a negligible or no yolk .

Thus the cleavage division in human is holoblastic i. e. it divides the zygote completely into daughter cells or blastomeres .

It is a series of mitotic division of zygote ,resulting increase in the number of cell .

These cells which becomes smaller with each cleavage divisions are know as blastomeres .

The first cleavage division occurs approximately 30 hours after fertilization to form two cell stage .

Approximately 40 hours after fertilization four cell stage occurs .And three days after fertilization 12-16 cell stage are formed .

Until the eight cell stage they form a loosely arranged clamp. After the third cleavage however blastomeres maximized their contact with each other forming a compact ball of cells held together by tight junction this process is called compaction .

The process compaction segregates inner cells which communicate extensively by gap junction from outer cells .

Approximately days after fertilization cell of the compacted embryo divided again to forma 16 cells morula .

The inner cell of the morula constitute the inner cell mass and surrounding cell compose the outer cell mass .

The inner cell mass gives rise to tissues of the embryo proper and the outer cell mass forms the  trophoblast which later contributes to form the placenta .  

IMMUNITY

 Immunity is the ability of an organisms to resist a particular infection or toxin by the action of specific antibodies .

  The immunity is two types 

 I- Innate immunity or non-specific defance mechanism

II- Acquired immunity or specific defence mechanism 

1- Innate immunity 

This type of immunity is present in an organisms by birth.

The innate immunity includes certain barriers and defence  mechanism that keep foreign particles out of the body .

 There are 4 types of barriers  

a- physical barriers

b- physiological barriers 

c- cellular barriers

d- cytokine barriers

a - physical barriers 

These includes the skin , nasal , hairs , mucous , membrane of nose ,respiratory tract and digestive tract.

These form the first line of defence .

They prevent the entry of pathogens into the body primarily .

b- physiological barriers 

These includes 

Lysozymes - These are present in tears and is bacteriolytic and digests the bacterial walls .

Acid in stomach - The HCL is secreted in side the stomach which kills most of the ingested microorganisms .

Saliva - The antibacterial properties of saliva prevent many harmful pathogens from eating the body .

 Cellular barriers - certain types of leukocytes of our body like polymorpho-nuclear leukocytes monocytes and natural killer in the blood as well as macrophages in tissues can phagocytocite and destroy microbes .

d- cytokine barriers 

virus infected cells secreted proteins called interferons which protect non-infected cells from further viral infection .

II- Acquired immunity 

The immunity which develops during lifetime by exposure to suitable foreign agents like microorganisms is called acquired immunity .

It is pathogen specific and is characterized by memory .

When the body first encounter a pathogen it produce a response which takes long time to developed and of low intensity called as primary immune response .

And if the body encounters the same pathogen second time it produce highly intensified and quick response called as secondary immune response .

The primary and secondary immune responses are carried out with the help of two special type of lymphocytes present in our blood .

They are a-  B-lyphocytes - These are produce from the bone marrow and get matured in the bone marrow .

They produce an army proteins in response to pathogens into our blood to fight with them called antibodies .

T-lymphocytes - These are produce from the bone marrow but they migrate to the thymus for maturation .

The T-cells themselves do not produce antibody but helps beta cells to produce them.   

    

GESTATION PERIOD OR PREGNANCY

The period of embryonic development in side the womb or uterus starting from fertilization of to birth or parturition is called gestation of pregnancy .

The human gestation period being with the last menstrual cycle and end with the birth of child .

The pregnancy or gestation period lasts about 9 month or 40 week or 280 days . The gestation period is divided into 3 trimester , consisting of 3 month each .

FIRST TRIMESTER 

It is consider 1st week to 13th week .

It is the initial period of development where the complex processes are being carried out .

These include the cleavage division , morula  and blastula formation , gastrulation ,formation of notochord.

Then the organogenesis bring about formation of organs and organ system from the three germ layers i.e. ectoderm , mesoderm and endoderm .

Limbs of the embryo big in to develop as well as the gonads  i.e. testis or ovary.

The baby heart begins to beat .

The nerves and muscles begin to work together . The make a first the eyelids close to protect the developing eye . They will not open again until week 28 .

At this time baby is about 7.5 C.M. long and weight almost 28 grams .

SECOND TRIMESTER

It is consider 14th week to 27th week.

Development of heart is improved or more and now it beats - 150 beats per minute .

The baby is more active . the mother might feel movement or kicking .

The eyes , nose , ears and face develop so that it begins to look like human .

The baby begins sucking motions with mouth .

Eye brows ,eye lashes ,fingernails and toenails have formed the baby can even scratch itself .

The babys bone marrow beings  to make blood cells . The hairs begin to grow baby head . The baby weight about 680 grams and 30 C.M. long .

THIRD TRIMESTER

It is consider 28th week to birth .

Rapid growth of the foetus takes place . The baby is getting bigger and has less space to move around .The movement are less forceful but the mother will still feel them .

Final differentiation of tissues and organs takeplace 

The development of  the brain is advanced .

Grasp and suckling reflexes are apparent . 

The baby bones are soft but fully formed . The eyes can open and close .

The baby organs are capable of  functioning on their own .As  the due date is near the baby may turn into a head down position for birth 

The average birth weight is between 2.8K.G. to 4.1 K.G. and  average length is 48 to 53 inches long .Most full term babies fall within  these ranges but healthy babies come in many different and sizes .     

    

OOGENESIS

 It is the process of production of eggs or ova from the germ cell which are derived from germinal epithelium of embryo .

The entire process of oogenesis divided into three phases .

1- Multiplication phase

2- Growth phase 

3- Maturation phase 

1 - Multiplication phase 

During this phase the primary germ cell divides mitotically to produce a large number of daughter cell called oogonia .

The oogonial cell contain diploid number of chromosomes  .

2 - Growth phase 

Phase of multiplication replaced by phase of growth .

Where oogonial cell is simple enlarged in size due to the absorption of nutritive material from the surrounding medium and also due to synthesis of nucleic acids and proteins .

After this changes each oogonial cell is then called the primary oocyte , having diploid number of chromosomes  .

3- Maturation phase 

During this phase the primary oocytes undergo reduction cell division .

The primary oocytes under go meosis -1 to form 2 unequal haploid daughter cell .

The large one is called as secondary oocyte and the smaller one is called first polar body .

The secondary oocytes then under goes meosis -2 to form 2 unequal haploid daughter cells. the larger one is called ovum or egg and the smaller one is called second polar body .  

GAMETOGENESIS

 It is the process of formation of gametes i.e. sperm and ovum in the gonads  i.e. testis and ovary .It involves two process .

1- SPERMATOGENESIS

2- OOGENSIS 

1- SPERMATOGENESIS

Spermatogenesis is the process of formation of sperm in the testis of male 

It involves two process

A - Spermatogenesis

B- Spermiogenesis 

A - Spermatogenesis

It is the formation of spermatids from primordial germ cells.

It is divided into three phase .

a- Multiplication phase 

b-Growth phase

c- Maturation phase

a-Multiplication phase 

It is the phase , primordial  germ cells divided repidly but mitotically to produce a large number of spermatogonia having diploid number of chromosome 

b-Growth phase 

During this phase the size of nucleus as well as spermatogonial cell enlarge .

This enlargement in the size of the cells due to absorption of nutritive material form adjoining cells and also due to synthetic activity of nuclei ,acid and proteins .

These enlarged cells are now called the primary spermatocyte again having diploid number of chromosome .

During this phase splitting of chromosomes . Linkage and crossing over also take place .

c- Maturation phase 

During this phase , the primary spermatocyte under go two successive reductional cell division .

First of fall it under go miosis -1 to form two equal but haploid cells called secondary spermatocytes.

These secondary spermatocytes undergo miosis-2 to form spermatids having haploid no of chromosomes .

 B- Spermiogenesis 

It is the formation of spermatozoa from spermatids .

This process involves the formation of head , neck , middle piece and  tail .

PNEUMONIA

Pneumonia is an infection in one or both lungs .

It can be caused by bacteria ,viruses or fungi .The bacterial pneumonia is the most common type in adults 

Pneumonia causes inflammation in the air sacs or alveoli of the lungs because the alveoli fills with fluidor pus , making it difficult to breathe .

The most common symptoms of pneumonia may include cough ,fever sweating ,chills shortness breath and chest pain.

Pneumonia can be classified according to an organisms that causes the infection .

1- Bacterial Pneumonia 

The most common cause of bacterial pneumonia is by streptococcus pneumonia .

Clamydophila pneumonia  and legionella pneumophila can also cause bacterial pneumonia .

2- Viral Pneumonia 

Respiratory viruses are often the causes of pneumonia ,especially in  young children and older people. It is usually not serious and lasts for a shorter time than bacterial pneumonia .

3- Mycoplasma Pneumonia 

The mycoplasma are not bacteria and viruses but have traits common to both .They can cause pneumonia in people  with chronic diseases or weakened immune system 

Example - pneumonia cjirovecil pneumonia 

 

RING WORM

It is a fungal infection  on the surface of the skin or scalp .

The medical term for ring worm tinea .The skin disease is further named for the site of the body where the infection occurs .

Some types of ring worm infection include .

Tinea beard-on the beard .

Tinea corporis - on the body .

Tinea pedis - infection of feet .

Tinea capitis - on the scalp .

Tinea craris - grain area .

Tinea facie - on the face .

The ring worm causes  a scally ,crusted rash that may appear as round , ring -likered patches on the skin .

The other symptoms and signs of ring worm include patches of hair loss or scaling on the scalp , itching and blister -like lesions .

Ring worm is contagious and can be passed through directly contact from person to person or by sharing combs , brushes , clothing and other personal care items .

Ring worm can be successfully treated with  antifungal medication used either topically or orally .

PREVENTION

The skin and feet has to be cleand  dry .

The clothing ,tovels , hair brushes , combs , headgear or other personal care items should not be shared .

Sandals or shoes are be used at gams , lockers and pools .

Touching of pets with bald spots can be avoided .