HUMAN REPRODUCTION AND REPRODUCTIVE HEALTH

Human reproduction

• Sexually reproducing

• Viviparous

• Reproductive events

1. Gametogenesis

2. Insemination

3. Fertilisation

4. Implantation

5. Gestation

6. Parturition

REPRODUCTIVE SYSTEMS

Male Reproductive System

• Location: Pelvis region

• Includes:

1. Pair of Testes

2. Accessory Ducts

3. Accessory Glands

4. External Genitalia

1) PAIR OF TESTES

• Location: Outside abdominal cavity within a pouch called scrotum

• Each testicle is oval in shape

• Length: 4-5 cm

• Width: 2-3 cm

• The testis is covered by a dense covering

• Each testis had about 250 compartments called testicular lobules

Seminiferous tubule:- lined on its inside by 2 type of cells

1. Male germ cells

2. Setolli cells

Interstitial Spaces: The regions located outside and between the highly coiled seminiferous tubules (regions surrounding the seminiferous tubules).

It contains:

1. Small Blood Vessels

2. Interstitial cells/Leydig cells

3. Immunologically Competent cells

2) ACCESSORY DUCTS

Includes:

1. Rete testis

2. Vasa Efferentia

3. Epididymis

4. Vas deferens / ductus deferens

5. Ejaculatory Duct (2): It acts as a tube (formed by the vas deferens and seminal vesicle duct) that transports sperm to the urethra. Each one receives sperm from its respective vas deferens along with secretions from the seminal vesicle on the same side. Both ducts empty into the single urethra. It also stores sperm

6. Urethra: Urethra passes through the corpus spongiosum (the column of spongy erectile tissue in the penis that surrounds the urethra) and its opening is known as urethral meatus, which lies on the tip of the glans penis

3) ACCESSORY GLANDS

1. Seminal Vesicles (Paired)

2. Prostrate Gland (Single)

3. Bulbourethral glands (paired) [Cowper's gland]

Seminal Vesicles (Paired)

Prostrate Gland (Single)

Bulbourethral Glands/Cowper’s Glands (Paired)

4) EXTERNAL GENITALIA

• Penis —> Cylindrical, muscular erectile organ formed with certain specialized erectile tissues to facilitate insemination.

• Penis —> Consists of a root, a body and the glans penis

• Root: Attached portion (Bulb of penis, Crus of Penis)

• Body of Penis

• Glans Penis—> distal enlarged end of penis [elongation of corpus spongiosum] and is covered with a fold of skin called the PREPUCE/FORESKIN.

IMPOTENCE —> Failure of erection of penis

HORMONAL CONTROL OF MALE REPRODUCTIVE SYSTEM

1. When puberty starts —> neurosecretory cells [in hypothalamus] increase their secretion of gonadotrophin-releasing hormone (GnRH).

2. GnRH —> stimulate the Anterior pituitary to increase its secretion of Luteinizing hormone (LH) & follicle-stimulating hormone (FSH)

3. LH —> Stimulates Leydig cells to secrete testosterone, synthesized from cholesterol.

4. Testosterone —> acts in a -ve feedback to suppress secretion of LH by anterior pituitary & GnRH by hypothalamic neurosecretory cells

5. Androgens —> stimulate process of spermatogenesis

6. FSH —> acts on Sertoli cells and stimulate secretion of some factors which help in the process of spermiogenesis

7. Once spermatogenesis is sufficient for male reproductive functions, Sertoli cells release inhibin, which reduces FSH secretion from the anterior pituitary.

8. Other effects produced by androgens

Female Reproductive System

• Location: Lower Pelvic region

• The female reproductive system includes:

1. Pair Of Ovaries

2. Accessory Ducts

(i) Oviduct

(ii) Uterus

(iii) Cervix

(iv) Vagina

3. External Genitalia

4. Accessory Sex Glands

(i) Bartholin / Greater Vestibular glands / Bulbovestibular glands

(ii) Skene’s/Paraurethral/Lesser Vestibular Glands

(iii) Mammary Gland

1) OVARIES

• Paired organs

• Primary sex organs

• Produce secondary oocytes and hormones like progesterone, estrogen, inhibin & relaxin.

• They arise from the same embryonic tissue as the testes and are the size & shape of almonds [greyish-pinkish structures].

• Length of Ovary: 2-4 cm

• Location: Either side of lower abdomen on either side of uterus

—> Connected to dorsal abdominal wall by MESOVARIUM ligaments

—> Connected to uterus by OVARIAN ligaments

• Blood vessels and nerves enter by mesovarium

• Each ovary is covered by,

—> Surface covering: Germinal epithelium (simple cuboidal mesothelium; modified peritoneum)

—> Just beneath epithelium: Tunica albuginea (dense connective tissue layer)

—> Ovarian stroma (internal):

• Cortex (outer/peripheral, dense): Contains ovarian follicles, corpus luteum, corpus albicans

• Medulla (inner, loose): Contains blood vessels, lymphatics, nerves, and loose connective tissue (no follicles)

• Surgical removal of ovaries—OOPHORECTOMY

• Oophorectomized female—Menstruation & ovulation absent

2) ACCESSORY DUCTS

(i)Oviduct:

• Known as the fallopian tube/Uterine tube

• Extends laterally from the uterus (extends from the periphery of ovary to uterus)

• Size: 10-12 cm long

• Lined internally by ciliated columnar epithelia.

• Removal of oviduct —> TUBECTOMY

• Divided into 3 Parts;

1. Infundibulum

2. Ampulla

3. Isthmus

• After ovulation, fimbriae sweep the secondary oocyte into uterine tube

• The ovum is taken to the uterus through peristaltic movement in the fallopian tube.

(ii) Uterus:

• Also called the womb/hystera/metra

• Location: B/w the urinary bladder and rectum

• Shape: Inverted pear

• Site for implantation & fetal growth & helps for placentation & expelling the baby during parturition.

• Surgical removal of the uterus - HYSTERECTOMY

• The uterine wall is divided into 3 layers

• (Uterus) Divided into 3 parts

1. Fundus

2. Body/Corpus [The uterine wall (especially of the body/corpus) is composed of three layers: perimetrium, myometrium, and endometrium.]

3. (iii) Cervix

(iv) Vagina

• Length: 8 - cm long

• Fibromuscular tubular canal that extends from the exterior (of the body, vulva) to the cervix (uterine).

• Tube - internally lined by non-keratinized stratified squamous epithelium

• The vaginal opening —> vaginal orifice.

1. Receptacle for the penis during coitus (receives)

2. Outlet for menstrual Flow

3. Passage for childbirth (made of smooth muscles)

• The vagina is highly vascular.

• Contains mucosa (mucous membrane) —> contains large amounts of glycogen —> decomposition of glycogen by lactobacillus bacteria produces organic acid —> thus causing acidic environment [which retards microbial growth & is harmful to sperm]

3) EXTERNAL GENITALIA

• Vulva/Pudenum

• Divided into 6 categories

1. MONS PUBIS

2. LABIA MAJORA

3. LABIA MINORA

4. CLITORIS

5. VESTIBULE

6. HYMEN

4) ACCESSORY GLANDS

(i) Bartholin / Greater Vestibular glands / Bulbovestibular glands⭐

• One pair of small alveolar glands present just b4 labia minora on each side of vaginal orifice

• Secretes mucus for lubricating the vagina during sexual stimulation, mating, parturition

(ii) Skene’s/Paraurethral/Lesser Vestibular Glands

• Pair of small glands near the external urethral opening

• Secrete fluid for urethral lubrication during arousal

• Homologous to the prostate gland

(iii) Mammary Gland

• Located in breasts

• Modified Sweat glands that produce milk

• Each breast has a pigmented projection - the nipple, which is surronded by a circular pigmented skin → areola

• Attached to thoracic wall through Pectoralis Major Muscle

• Each mammary gland consists of 15-20 lobes

• Each lobe is divided into smaller lobules(many) inside which milk producing alveoli are found

• The alveoli cells secrete milk which is stored in the lumen of alveoli

• Mammary tubules arise from each individual lobule and carry milk from alveoli to larger ducts.[The alveoli open into mammary tubule]

• The tubule of each lobe/lobule join to form Mammary duct

• Several mammary ducts join to form many mammary ampulla located just below nipple

• Ampulla is connected to 15-20 number of lactiferous ducts that opens to exterior through nipple through which milk is sucked out.

• LACTATION: Sythesis, secretion and ejection of milk [ Process of milk production, secretion, and release from the mammary glands.]

• GYNAECOMASTIA: Development of breast in males

• MASTECTOMY(Female): Surgical removal of breasts

HORMONAL CONTROL OF FEMALE REPRODUCTIVE SYSTEM

• GnRH is secreted by the hypothalamus which stimulates the anterior pituitary to secrete LH and FSH

• FSH —> stimulate growth of ovarian follicle , also increases the development of egg/oocyte within the follicle to complete the meosis 1 to form secondary oocyte

• FSH also stimulates follicular cells in formation of estrogen

• LH —→ stimulates the Corpus Leuteum to secrete progestrone and inhibin

• Rising levels of progestrone & estrogen inhibit oversecretion of FSH , LH and GnRH(-ve feedback)

REPRODUCTIVE EVENTS

1) GAMETOGENESIS

Spermatogenesis

• Begins at puberty

• It occurs in 2 Different Stages

A) Formation of Spermatids

1. Multiplication Phase

• Spermatogonia multiply by more and more mitotic division and increase in number(Type A and Type B)

• Diploid spermatogonia undergo repeated mitosis to produce Type A cells that remain as stem cells and Type B cells that move on to become sperm.

2. Growth Phase

• Type B spermatogonia significantly increase in size (by accumulating nourishing materials) and prepare for meiosis by transforming into primary spermatocytes.

3. Maturation Phase

a) Meiosis - 1

• Primary spermatocyte undergoes Meiosis 1 —> formation of two haploid cells called Secondary Spermatocytes

b) Meiosis - 2

• Secondary spermatocytes undergo second meiotic division to form four haploid spermatids

B) Spermiogenesis

• Differentiation of spermatids to spermatozoa by the process of metamorphosis called spermiogenesis( during spermiogenesis sperm heads embed to Sertoli cells - allows the Sertoli cells to provide vital nutrients, structural support, and maturation signals)

• Spermiation is the subsequent release of these mature spermatozoa from Sertoli cells into the lumen.

Spermatid → (attached to Sertoli cells during spermiogenesis) → differentiates into spermatozoa (gain nutrients from sertoli cells) and become mature spermatozoa → spermiation (release into lumen)

Oogenesis