Grade 12 Zoology Note

Reproductive system

Reproductive system of human

 It is a natural phenomenon by which organism reproduce young ones of their  own kinds for continuation of race. Human beings are unisexual or dioecious i.e. male and female reproductive system is separated in separate individual.

 

Male reproductive organs

 

     1.Testes (one pair)

     2.Epididymis (one pair)

     3.Vasa deferens (one pair)

     4.Ejaculatory duct (one pair)

     5.Urethra.

     6.Penis.

     4.Accessory glands.

 

fig:male reproductive organs

 

1.Testes: These are pinkish-oval lie inside the scrotum. The scrotum lies outside the abdominal cavity. So that temperature of testes remains 2.30c below than temperature of body. Which is needed to produces sperm.

Microscopic structure: 

There are three layers to cover testis. These are Outer-tunica vaginalis, Middle-tunica albugania and Inner-layer-tunica vasculosa.

 http://4.bp.blogspot.com/-KLlHlg9PySA/VKa8NRSDClI/AAAAAAAAAJU/bej_x-Keg5s/s1600/clip_image002198.jpg

 

fig:T.S. of testis

There are 200-300 testicular lobules in testis. Each lobule is composed of 1 to 4 coiled seminiferous tubules. The tubules are lined with germinal epithelial cells (spermatogonia).These epithelial cells produce sperms by the process of spermatogenesis. Sertoli cells supply nourishment to develop sperms.

There are interstitial cells (cells of leydig) in between seminiferous tubules and connective tissue. The interstitial cells produce androgens, which promotes development of male accessory glands and controls male sex features (moustache, beard, change of voice)

2.Epididymis: 

It is funnel like convoluted about 6 meters long tube. Board part of anterior epididymis is called caput epididymis. Middle narrow part is corpus epididymis posterior end is cauda epididymis.

Function:

Store the sperm and secrets fluid to nourish sperm.

 

3.Vasa deferens: 

It arises from cauda. It forms a loop around urinary bladder and joins with duct of seminal vesicle. It form ejaculatory duct with seminal vesicle.

Function: 

carry sperm from testis to seminal vesicles.

4.Ejaculatory duct: 

There  are two short formed by the union of duct from a seminal vesicle and vasa deferens, there carry the mixture of sperm and secretion of seminal vesicle.

5.Urethra:  

It is 20 cm long arises from urinary bladder. It discharges urine and semen both.

6.Penis: 

It is copulatory organ of human. It is made up of three columns of spongy tissues (two dorsal cavernosa and one ventral corpora spongiosum). Enlarged-tip of penis is called glans penis which is highly sensitive. Penis deposits the semen in vagina with spermatozoa.

 Accessory glands: 

It consists of;

a.Seminal vesicles: 

These are two pouches like below-posteriorly of urinary bladder and opens into ejaculatory duct.  These secret and expel a viscous fluid which keep sperms alive.

      b. Prostate gland: 

     It lies behind urinary bladder. It is secretes thin milky substance occupy about 30% volume of semen.

      c.Cowper’s glands:

      The paired glands lie below the prostate glands. Their alkaline secretion lubricates the semen flow.

      d.Eretion of penis: 

     Erection is caused by dilation of blood vessel of blood vessel resulting collection of more blood spaces of spongy tissue. About 3ml of semen is discharged by penis in each ejaculation during copulation.

 

Female reproductive organs: Female reproductive organs’ consists of  following;

FIG: female reproductive organs

1.Overies:

There is one pair of about 3.5cm long, pink, almond shaped and situated in          

abdominal cavity on either side of vertebral column. Each kidney is attached with ovarian ligament and body wall with mesovarian fold with ovaries. Internally each          ovary is differentiate with

      i.Outer germinal epithelium (cubical)

      ii.Tunica albunginea: connective tissue below germinal epithelium.

      iii.Stroma: Inner mass of connective tissues made up of cortex medulla.

     

      When Graafian follicle liberates ovum it is called corpus luteum. The corpus luteum secrete progesterone hormone in the influence of luteinizing hormone. The hormones thicken the endometrium wall and activate the mammary gland for their development.

http://3.bp.blogspot.com/-4g2vzmcxUxQ/VKa8lJjNHyI/AAAAAAAAAJw/NZ88ig4qFR4/s1600/256.jpg

fig; T.S of ovary

 

     2.Fallopian tubes (oviducts): these are ciliated tubes of 10-20cm long arise from uterus.

It has four parts:

     a.Funnel like infundibulum near ovary with finger like structure fimbriae

     b.Wide curved part ampulla.

     c.Narrow part isthmus.

     d.Part near uterus (uterine).

 

      3.Uterus:  it is a pear shaped hollow muscular organ. Upper dome shaped part is called fundus. Main part is called body of uterus. Lower portion of uterus is called cervix.

     4.Vagina: It is female copulatory organ. It is tubular, about 10cm long. It passage for menstrual flow and receptor of spermatozoa. In virgins the vaginal orifice is partially covered by hymen membrane.

      5.Vulva: It is external genitalia it is consists of mons pubis (hair part) clitoris (erectile organ) labia major a (inner fold of vulva). Libia minora have in more number.

      6.Accessory glands: 

      These consists of Bartholin’s glands and mammary glands. 

     

Bartholin’s  glands:

      These are two bean-shaped lie on either of side of vaginal orifice These glands secret viscid fluid for lubricant of vulva during sexual intercourse and sexual excitement.


Mammary glands: 

      These are pair rounded with median nipple. Each gland made up of 15-25 lobules of milky glands. Each gland sends a lactiferous duct toward nipple. Milk gland produce milk under the control of prolactin and ejection of milk is controlled by pituitary gland.

 

Menstruation (ovarian) cycle: 

It is cyclic changes occur in reproductive tract of human female on a period of 28 days. It is confirmed by loss of vaginal blood. It occurs at about 13 years of age till the age of 50-55 years. The menstruation is seen in human monkeys, gorilla etc. The menstrual cycle is categorized into three phases;

 

     1.Menstrual phase; 

     It is the phase of blood flow. It last for 3-5 days. It is caused due to cast off epithelia lining of endometrium. Oestrogen and progesterone is very law in the blood. Menstruation is observed only when ovum remains unfertilized.

     2.Proliferative or follicle phase:

          1.Number of endometrium phase. It is last of endometrium in the phase. It last for

          9-10 days( 5th -14th ) day.

          2.The release of FSH from pituitary stimulates the development of follicles of

          ovary.

          3.Ovarian follicle matured into griffin follicle and secrete oestrogen hormone

          which increases up to 12th days.

          4.Oestrogen enhances proliferation of cells of endometrium of uterus and

           fallopian tubes (up to 2-3mm thickens). The wall is highly supply with blood

          vessels and ready for implantation.

          3. Secretory or luteal or ovulatory phase

          1.It last for about 12-14 days (14th- 28th day of menstrual cycle).

          2.LH (lutening hormone) is secreted by pituitary gland called luteal phase.

          3.LH and FSH stimulate the ovulation (releases of ova).so that LH and FSH

          concentration become high at this time.

          4.After ovulation follicles of ova (corpus luteum) secret progesterone hormone.

          5.Progesterone inhabits maturation of any follicle and ovulation.

          6.Progesterone stimulates thickening of endometrium for implantation of zygote.

          It also stimulates to secret water mucus and also affects mammary glands.

         Menopause:

          It is phase of women’s life. It occurs between 50 to 55 years. At that age ovaries

           are less responsive to FSH and LH. Ovulation and menstrual cycle becomes irregular and stop. After the menopause female loses the ability to reproduce progesterone and oestrogen hormone becomes imbalance.


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