Introduction to Embryology Introduction to Embryology &&

Reproductive System Reproductive System

Human EmbryologyHuman Embryology

The science concerned with origin & development of human being from Zygote (?) to birth (prenatal development)

Stages of Human Development:

1. Prenatal development (before birth)

2. Postnatal development (after birth)

Birth: a dramatic event during development that results in a change in environment.

TerminologyTerminology

Oocyte (ovum):

The female sex cell (gamete) that develops in ovaries

Sperm:

The male sex cell (gamete) that develops in testes

Gamete:

The germ cell of male or female that have the half number of chromosomes (Haploid, 23)

Fertilization (Conception):

The union of male gamete with female gamete to form a zygote (diploid, 46)

Dizygotic twins: Non-identical twinsProduced from independent release of 2 oocytes & subsequent fertilization by different sperms.

Monozygotic twins:Identical twinsProduced from the separation of the Zygote within the first week of fertilization (~8 days)

*if the separation happened later than 8 days ??

Cleavage:Mitotic cell division of the zygote to form blastomeres

Blastomeres:The emberyonic cells formed by cleavage (division) of the zygote

Morula:When 12 or more blastomeres have formed

berry-like shape (L, mulberry)3-4 days after fertilizationwithin uterine tube

Blastocyst:After the morula reaches the uterus uterine fluid passes into the morula forming a fluid-filled cavity

morula becomes = blastocyst

BlastocystBlastocyst

Early blastocyst:

cavity in center (usually)

Late blastocyst:

blastomeres separated into:

1. Trophoblast:

outer cell layer = placenta

2. Inner cell mass:

a group of blastomeres gathered at periphery

give rise to the embryo = embryoblast

Implantation:Attachment of the blastocyst to endometrial wall of the uterus

starts 6-7 days after fertilization (end of 1st wek)

Embryo:The developing human during early stages of prenatal

development (first 2 months)

embryonic period: day 1 end of 8th week

Fetus:The developing human after 8 weeks & until birth

Infant: ? (L, infans)

Neonate: ? (L, newborn)

Crown-Rump Length (CRL)Crown-Rump Length (CRL)

The measurement of the length of the embryo or fetus from vertex of skull (crown of head) to the rump (buttom of buttock)

“the sitting height”

Male Reproductive SystemMale Reproductive System

Scrotum & Testes

System of Ducts:Epididymis & Vas deferensejaculatory duct, urethra

Accessory sex glandsSeminal vesiclesProstateBulbourethral glands

Penis

ScrotumScrotumSupporting sac

Layers:

1. Skin (thin layer)

2. Superficial fascia

3. External spermatic fascia

4. Cremasteric fascia

5. Internal spermatic fascia

Contents:

1. Testes

2. Epididymis

3. Lower end of spermatic cord

Testes (testicles):

Oval glands where sperms are formed (spermatogenesis)

lf. Testis lies at lower level than Rt. One

Epididymis:

The place where sperms are stored & mature

head, body & tail

Vas (ductus) Deferens:

The tube that carries the sperms from epididymis to ejaculatory duct ( 0.5 m)

Accessory Sex GlandsAccessory Sex GlandsSeminal Vesicles

Post. to urinary bladder (on each side)

Secrete alkaline (?) viscous fluid containing fructose (?)

60% of S.F.

Prostate glandInf. to urinary bladderSecretes milky fluid containing

proteolytic enzymes (?) 25% of S.F.

Bulbourethral glands(Cowper’s glands)

Inf. To prostateSecrete alkaline fluid & mucus

The PenisThe Penis

The male reproductive organ

Consists of:

Root body Glans penis

3 cylindrical masses of tissue:

corpus cavernosum (2)

corpus spongiosum (1)

Circumcision?

Surgical removal of extra skin covering the glans (foreskin)

Female Reproductive SystemFemale Reproductive System

Ovaries

Uterus & Uterine tubes

Vagina

External Genitalia

(Vulva)

OvariesOvaries

Almond-shaped reproductive glands

On the lat. Walls of the pelvis

Fxn.:

production of Oocytes

secretion of estrogen &

progesterone

Uterine TubesUterine Tubes

Fallopian tubes, oviducts

uterus lat. ovaries

4 parts:

Infundibulum (funnel-shaped)

Ampulla (site of fertilization)

Isthmus

Uterine part (intramural)

UterusUterus

The site for prenatal development & growth

8 cm in length & 5-7 cm in width

Consists of:

Fundus

Body

Cervix:

internal os

external os

Walls of The UterusWalls of The Uterus

Perimetrium:

Thin layer of C.T.

(serosa or adventitia)

Myometrium:

Thick smooth m. layer

Endometrium:

Basal layer

Functional layer:

disintegrates during menstruation

VaginaVagina

Communicating elastic tube (8cm) between the Vulva & Uterus

Ascends upward & backward (45o)

Fxn.:

1. Excretory passage for

Menstrual fluids

2. Receives the penis during

sexual intercourse

3. Inf. part of the birth canal

Vulva (Ext. Genitalia)Vulva (Ext. Genitalia)

Composed of 4 parts:1. Labia majora:

folds of skin & fatty layerfxn.?

2. Labia minorafolds of skin surround the vaginal orifice

3. Clitoris:small erectile organat sup. jxn. of minoraglans clitoris equivalent to glans penis in male

4. Vestibule:urethral & vaginal orifices