SEX CELL DIFFERENTIATION

OOGENESIS – EGG DIFFERENTIATION

SPERMATOGENESIS – SPERM DIFF.

◦ SPERMIOGENESIS – TRANSFORMATION OF THE MALE GAMETE

IN MAN/MAMMALS, PRIMORDIAL GERM CELL COMES FROM YOLK SAC ENTODERM NEAR CAUDAL END OF BODY

FROM THERE THEY MIGRATE FORWARD THROUGH THE MESENCHYME OF THE MESENTERY AND INTO THE GENITAL RIDGE WHICH SOON BECOMES THE SEX GLAND

THEN PROLIFERATION

PROLIFERATION IS PERIODIC (MONTHLY IN FEMALES) URING THE POTENTIAL CHILD-BEARING YEARS

CELL PROLIFERATION – PRIMITIVE CELL REPEATEDLY DIVIDES

PERIOD OF GROWTH – RAPID ENLARGEMENT OF THE CELLS PRODUCED

PERIOD OF MATURATION – NUCLEAR CHANGES LIMITED TO THE FINAL TWO DIVISIONS

ORIGIN OF THE FOLLICLES

◦ PRIMORDIAL CELLS (OOGONIA) PROLIFERATE WITHIN THE CORTEX OF THE OVARY

◦ SMALLER EPITH. CELLS, OF GERMINAL-EPITH ORIGIN ENCASED THE OOGONIA AND PRODUCED PRIMARY FOLLICLE

◦ AFTER BIRTH, FORMATION OF HUMAN OOGONIA STOPS THEN CELLS ARE NOW CALLED OOCYTES

370,000 – AT BIRTH

190,000 – AT PUBERTY

26,000 – AT AGE 30

AFTER 30 OR MORE YEARS (CHILD-BEARING SPAN), FOLLICLES WILL NO LONGER BE SEEN

NO ADVANCE BEYOND THE STAGE OF THE PRIMARY FOLLICLE UNTIL PUBERTY (14TH YEAR)

FEW HUNDREDS OF OOCYTES ARE LIBERATED PERIODICALLY DURING OVULATION

GROWTH OF FOLLICLE STARTS SLOWLY BUT GROWS RAPIDLY 1-3 DAYS PRIOR TO RUPTURE

MATURATION – ACHIEVED BY MEIOSIS WITH 4 CELLS HAVING EQUAL NUCLEI WHILE THE CYTOPLASM IS UNEQUALLY DIVIDED

1 LARGE RIPE OVUM 3 RUDIMENTARY OVA (POLAR BODIES) OR

POLOCYTES CYTOPLASM – GRANULAR AND

CONTAINS FEW TO MANY INERT GRANULES

YOLK/DEUTOPLASM – MADE UP OF FATTY AND ALBUMINOUS SUBSTANCE; SERVES AS NOURISHMENT FOR THE EMBRYO

YOLK – USEFUL IN CLASSIFYING EGGS.

I. BASED ON RELATIVE ABUNDANCE OF YOLK:

1. SMALL

2. MEDIUM

3. LARGE

II. DISTRIBUTION OF YOLK IN CELLS:

1. ISOLECITHAL – EQUAL YOLK

MEIOLECITHAL – LITTLE YOLK

- INVERTEBRATES

- ALL MAMALS EXCEPT LOWEST FORMS

2. TELOLECITHAL EGGS – ABUNDANT YOLK AND CONCENTRATED IN ONE HEMISPHERE

-INVERTEBRATES

-ALL VERTEBRATES LOWER THAN MARSUPIALS

- CHICK EGG

3. MEDIALECITHAL (MEDIUM YOLK) –MODERATE YOLK – AMPHIBIANS

4. MEGALECITHAL- LARGE, YOLK RICH EGGS OF BONY FISHES , REPTILES , BIRDS

5. CENTROLECITHAL- DISTINCTIVE ARRANGEMENT OF YOLK, MASSED CENTRALLY BUT SORROUNDED BY A PERIPHERAL SHELL OF CLEAR CYTOPLASM.

EGG POLARITY:

ANIMAL POLE – SITE WHERE POLAR BODIES PINCH OFF

- VIGOROUS PART IN DEVT. & WHERE HIGHEST CAPACITY FOR ACTIVITY RESTS

- VEGETAL POLE- SLUGGISH END OF CELL AND CONCERNED WITH THE DEVT. OF NUTRITIVE ORGANS

- YOLK LADEN

PROTECTIVE MEMBRANES:

1° MEMBRANE-CELL/PLASMA MEMBRANE

2° MEMBRANE- ZONA PELLUCIDA

3° MEMBRANE –ADDED BY THE OVIDUCT

AS THE EGG PASSES THROUGH IT

- JELLY OF FROG’S EGGS

- ALBUMEN OF RABBIT’S EGG

- ALBUMEN AND SHELL OF HEN’S EGG

CELLULAR CORDS ( GERMINAL EPITHELIUM)

TESTES TUBULES

SPERMATOGONIA (STEM CELLS)- LARGER

INDIFFERENT CELLS- SMALLER

PUBERTY – SOME SPERMATOGONIA REMAIN AS STEM CELLS WHILE OTHERS BECOME PRIMARY SPERMATOCYTE-2°SPERMATOCYTE-SPERMATID-SPERM

DETACHED FROM SERTOLI CELLS AND ARE SET FREE INSIDE THE SEMINIFEROUS TUBULES

SPERM CELL- SMALLEST CELL IN MASS MADE UP OF HEAD, NECK & TAIL.

AT THE END OF MATURATION (MEIOSIS)

THE DEVT. OF EGG IS COMPLETE AND THE EGG BECOMES FUNCTIONAL WHILE THE MALE GAMETE UNDERGOES A SERIES OF TRANSFORMATIONS BEFORE A FUNCTIONAL SPERM CELL IS DERIVED

CHROMOSOME NUMBERS

(2N) MAN=46 (DIPLOID CHROMOSOME#)

(N) MAN=23 (HAPLOID CHROMOSOME#)

FEMALE -22 ORDINARY CHROMOSOME PAIR

-23RD PAIR(SEX CHROMOSOME)

(XX) PAIR

MALE

22 ORDINARY CHROMOSOME PAIR

23RD PAIR (XY) PAIR

24 DIFFERENT KINDS OF CHROMOSOMES

COMPARISON OF EGG & SPERM OF ANIMALS IN GENERAL

FEATURES OVUM SPERMATO-ZOON

SIZE LARGE SMALL

SHAPE SPHEROIDAL ELONGATED

QUANTITY FEW (ONE) OFTEN IN MILLIONS

MOTILITY NON-MOTILE VIGOROUS(FLAGELLATE)

PROTECTION EGG ENVELOPES

NONE

CYTOPLASM BULKY MINIMAL

YOLK LITTLE TO MUCH

NONE

CENTRO-SOME

DISAPPEARS RETAINED –CENTRIOLE &

AXIAL FILAMENT

MITOCHON-DRIA

DIFFUSED IN THE BODY ONLY

GOLGI-APPARATUS

DIFFUSED IN ACROSOME

ONLY

NUCLEUS OPEN STRUCTURED

CONDENSED AS SPERM

HEAD

NUCLEOLUS TYPICAL INDISTINGUISHABLE

SEX DETERMININ

G ROLE

RARELY TWO KINDS(MOTH

S/BIRDS)

USUALLY TWO

KINDS(MALE&FEMALE)

INTERNAL FERTILIZATION

-SMALL NUMBER OF EGGS

EXTERNAL FERTILIZATION

-LARGE VOLUME OF EGGS

TYPES OF BREEDING:

• CONTINUOUS-ALL THOUGHOUT THE YEAR

• SEASONAL/ANNUAL SPAWNING PERIOD

• SPONTANEOUS- SEXUAL EXCITEMENT/PERIOD OF HEAT / ESTRUS

• PROVOKED OVULATION- INDUCED BY THE ACT OF COPULATION.

• PERIODIC (INTERVALS OF 4 WEEKS) SPONTANEOUS

HUMAN FEMALE

-OVULATION (14 YRS.) + 30 YEARS OF SEXUAL ACTIVITY

FOLLICLE RUPTURE- SIMILAR TO THE RUPTURE OF A BOIL; TAKES PLACE AT THE STIGMA

- HORMONAL FACTOR AND LOCAL WEAKENING OF FOLLICULAR WALL

EGG TRANSPORT- MADE POSSIBLE BY HORMONAL CONTROL AND OVARY ACTIVITY.

TIME OF OVULATION- MIDDLE OF THE CYCLE

28-DAY CYCLE

26-DAY CYCLE

30-DAY CYCLE

EGG VIABILITY- FERTILIZABLE PERIOD IS LESS THAN ONE DAY – GENERATION TAKES PLACE

CORPUS LUTEUM- OVARIAN STRUCTURE (COLLAPSED & FOLDED) VESICULAR

FOLLICLE- MADE UP OF LUTEIN CELLS• CORPUS LUTEUM OF OVULATION• CORPUS LUTUEM OF PREGNANCY• CORPUS ALBICANS- WHITE SCAR LEFT

MADE UP OF FIBROUS TISSUE.

• PSEUDOCOPULATION- INCREASES CERTAINTY OF UNION

• COPULATION- SEXUAL EMBRACESPERM STORAGE- ACCUMULATION AT

EPIDIDYMIS(TRAVERSED IN 12 DAYS)SPERM DISCHARGE- EJACULATION(MALE

CLIMAX DURING COITUS) SEMEN (SPERMATOZOA PLUS THE

SECRETIONS FROM 3 ACCESSORY GLANDS:

• SEMINAL VESICLE

• BULBO-URETHRAL GLAND

• PROSTATE GLAND

3 ML EJACULATE-250,000,000 SPERMS

SPERM TRANSPORT-LASHING, FLAGELLATED MOVEMENT ; WILL TRAVERSE UTERUS IN 70 MIN.(7 INCHES)

SPERM VIABILITY= 1-2 DAYS

IN VITRO- TWO WEEKS

HUMAN SEMEN(FROZEN IN GLYCEROL

AT - 70℃ (CAN SURVIVE FOR MANY MONTHS

PROCESS WHEREBY 2 GAMETES FUSE TOGETHER TO CREATE A NEW INDIVIDUAL WITH A GENOME DERIVED FROM BOTH PARENTS

ACCOMPLISHES 2 SEPARATE ENDS; SEX (THE COMBINING OF GENES DERIVED FROM 2 PARENTS) AND REPRODUCTION (THE CREATION OF A NEW ORGANISM)

CONCEPTION CONSISTS OF 4 MAJOR EVENTS:

1. CONTACT AND RECOGNITION BETWEEN SPERM AND EGG. THIS ENSURES THAT THE SPERM AND EGG ARE OF THE SAME SPECIES

2. REGULATION OF SPERM ENTRY INTO THE EGG. ONLY ONE SPERM CAN ULTIMATELY FERTILIZE THE EGG. THIS IS USUALLY ACCOMPLISHED BY ALLOWING ONLY ONE SPERM TO ENTER THE EGG AND INHIBITING ANY OTHERS FROM ENTERING

3. FUSION OF THE GENETIC MATERIAL OF SPERM AND EGG

4. ACTIVATION OF EGG METABOLISM TO START DEVELOPMENT

ANTON VAN LEEUWENHOEK – CO-DISCOVERER OF SPERM

NICOLAS HARTSOEKER – CO-DISCOVERER OF SPERM

DREW A PICTURE OF A PREFORMED HUMAN (HOMUNCULUS)

BELIEF THAT THE SPERM CONTAINED THE ENTIRE EMBRYONIC ORGANISM

POOLING TOGETHER OF SPERM AND EGG NUCLEI

• INVERTEBRATES ( ROTIFERS, CRUSTACEANS INSECTS) DEVELOP WITHOUT THE BENEFIT OF FERTILIZATION(PARTHENOGENESIS)

RESULTS OF FERTILIZATON:

1. REASSOCIATION OF MALE AND FEMALE SETS OF CHROMOSOMES , RESTORING THEM TO THE FULL DIPLOID NUMBER.

2. SEX DETERMINATION

3. ACTIVATION OF OVUM INTO CELL DIVISION OR CLEAVAGE.

SEX DETERMINATION – IS ESTABLISHED AT THE TIME OF FERTILIZATION

DURING MEIOSIS, CHROMOSOME NUMBER IS HALVED

22+X – FEMALE

22+X – MALE; 22+Y – MALE

22+X + 22+X = 44+2X

22+X + 22+Y = 44+X+Y

PERIODS OF EARLY DEVELOPMENT:

1) GAMETOGENESIS

2) FERTILIZATION

3) CLEAVAGE

4) GASTRULATION

FERTILIZED EGG-MANY CELLED INDIVIDUAL(CLEAVAGE) - CELLS TYPICALLY ARRANGE THEMSELVES INTO A HOLLOW SPHERE, THE BLASTULA

CELLS OF BLASTULA- REDISTRIBUTED AS THE PRIMARY GERM LAYERS(GASTULATION)

IT CONTAIN THE MATERIAL OUT OF WHICH THE EMBRYO AND ALL ITS PARTS WILL DIFFERENTIATE.

• ECTO

• MESO

• ENTO/ENDODERM

THE VERTEBRATE GROUPS

I. ANAMNIOTA- WITHOUT AMNION

FISHES-LAMPREY , STURGEON,SHARK,BONY FISHES

AMPHIBIANS-FROGS,TOAD,SALAMANDERS

II. AMNIOTA- WITH AMNION

REPTILES

-LIZARD,CROCODILES,SNAKES,TURTLES

MAMMALS – HAIR AND MAMMARY GLANDS

• MONOTREMES- DUCK-BILL /ECHIDNA• MARSUPIALS-OPOSSUM/ KANGAROO• PLACENTALS-YOUNG NOURISHED IN THE

UTERUS VIA PLACENTA • PRIMATES- WITH NAILS

(LEMUR,MONKEY,APE AND MAN) –SUBORDER ANTHROPOIDA

-DOUBLING/FRACTIONATING PROCESS PRODUCING COHERING,STICKY, BLASTOMERES ARRANGED AROUND A CENTRAL,FREE SPACE(BLASTOCOELE)

EGG CLASSIFICATION ON THE BASIS OF ABUNDANCE AND YOLK DISTRIBUTION:

A. TOTAL- HOLOBLASTIC OVA; ENTIRE OVUM DIVIDES

1. EQUAL-ISOLECITHAL OVA

-EQUAL SIZED BLASTOMERES

• AMPHIOXUS/MARSUPIAL/PLACENTAL MAMMALS

2. UNEQUAL- MODERATELY TELOLECITHAL OVA

• LOWER FISHES / AMPHIBIANS

B. PARTIAL- MEROBLASTIC OVA; ONLY PROTOPLASMIC REGION DIVIDES.

1. DISCOIDAL-HIGHLY TELOLECITHAL OVA

-MITOSIS RESTRICTED TO THE ANIMAL POLE.

• HIGHER FISHES/REPTILES/BIRDS/

MONOTREME MAMMALS

2. SUPERFICIAL – CENTROLECITHAL OVA; DIVISION RESTRICTED TO THE PERIPHERAL CYTOPLASMIC INVESTMENT

• ARTHROPODS

AMPHIOXUS-FISH-SHAPED; LOW CHORDATE

AMPHIBIANS REPTILES/ BIRDS MAMMALS

- FISH SHAPED; LOW CHORDATE

- EARLY STAGES OF DEVT. IS SIMILAR TO SOME INVERTEBRATES

- ISOLECITHAL EGGS

- CLEAVAGE IS TOTAL AND NEARLY EQUAL

- SUBSEQUENT CELL DIVISIONS IN ALTERNATE PLANES PRODUCES 32,64 ANO 128 CELL STAGES

- SIZE OF CELLS ARE PROGRESSIVELY DIMINISHED WHILE THE CENTRAL CAVITY ENLARGES TO FORM THE BLASTOCOELE

MODERATELY TELOLECITHAL (FAIR AMOUNT OF YOLK)

- CLEAVAGE IS TOTAL BUT UNEQUAL

- UPPER 4 MICROMERES ARE SMALLER THAN THE LOWER 4

- FORMS A CENTRAL BLASTOCOELE WHERE BLASTOMERES AT THE ANIMAL POLE ARE SMALLER; LARGER & FEWER AT VEGETAL POLE

WALL IS MORE THAN 1 CELL THICK

BLASTOCOELE IS RELATIVELY SMALL; LOCATED ABOVE CENTER DUE TO THE THICK WALL OF THE VEGETAL POLE

WITH LARGE EGGS

- CLEAVAGE IS PARTIAL & DISCOIDAL

- PRODUCES A DISCOIDAL PLATE OF CELLS PERCHED ON THE SURFACE OF THE YOLK AND SEPERATED FROM IT BY A CLEFT

- CLEAVAGE PRODUCES A MODIFIED BLASTULA( DISCOBLASTULA) WITH THE CELLULAR CAP CALLED A BLASTOCOELE

MARSUPIAL & PLACENTAL MAMMALS HAVE EMBRYOS THAT ARE DEVELOPED WITH DEPENDENCE ON THE MOTHER.

- EGGS ARE ISOLECITHAL- CLEAVAGE TAKES PLACE IN THE ZONA

PELLUCIDA & THE BLASTOMERES ACCOMMODATE THEMSELVES TO THE SPHEROIDAL CAVITY.

- CLEAVAGE IS TOTAL AND NEARLY EQUAL/

- DIVISION BEGINS IN THE UTERINE TUBE & COMPLETED IN THE UTERUS

- COMPLETED WITHIN A RANGE OF 70 HRS.(RABBIT) TO 190 HRS. FOR THE COW.

INVOLUTION , ELONGATION & CONVERGENCE

- CHARACTERIZE GASTRULATION IN ALL CHORDATES

ANIMAL TYPE

TYPE OF EGG

CLEA-VAGE

BLAS-TULA

BLASTU-LA CAVITY

METHODS OF GASTRULATION

COMMENT ON GASTRULATION

AMPHIOXUS

ISOLECITHAL (LITTLEYOLK)

TOTAL;EQUAL

SPHERE;WALL A SINGLE LAYER

SPHERI-CAL RELATIVELY LARGE

INVAGI-NATION; INVOLU-TION VIA BLASTO-PORE

EARLY INNER LAYER IS A COMPO-SITE

AMPHI-BIANS

TELOLE-CITHAL(MODE-RATE YOLK)

TOTAL;UNEQUAL

SPHERE; WALL LAYERED;THICK-NESS VARIES

SPHERI-CAL; RELATIVELY SMALL;ECCEN-TRIC

CHIEFLY IN VOLU-TION VIA BLASTO-PORE

INVOLU-TED LAYERS ARE SEPARA-TE FROM START

BIRDS TELOLE-CITHAL(MASSIVE YOLK)

PARTIAL;DISCOI-DAL

CELL-DISC;BLASTO-DERM)LIES ON MASSIVE YOLK

SHA-LLOW;DELAYED UNTIL ENTO-DERM FORMS

DELAMI-NATION;INVOLU-TION VIA PRIMI-TIVE STREAK

OCCURS IN TWO STAGES;MODI-FIEDAMPHIBIAN STYLE

MAMALS(EXCEPTLOWEST)

ISOLECI-THAL(LITTLE YOLK)

TOTAL;EQUAL

BLASTO-CYST, WITH INNER CELL MASS

MERGEDWITH YOLK-FREE BLASTOCYST CAVITY

DELAMINATION;INVOLU-TION VIA PRIMI-TIVE STREAK

OCCURS IN TWO STAGES;BASICA-LLYSIMILAR TO BIRDS

ECTODERM MESODERM(INCLUDING

MESENCHYME)

ENTODERM

1. EPIDERMIS,INCLUDING: CUTANEOUS GLANDS HAIR, NAILS &LENS

2. EPITHELIUM OF: SENSE ORGANS. NASAL CAVITY;SINUSES.MOUTH , INCLUDING: ORAL GLANDS; ENAMEL,

1. MUSCLE(ALL TYPES)

2. CONNECTIVE TISSUE ; CARTILAGE;BONE;NOTOCHORD

3. BLOOD;BONEARROW

4. LYMPHOID TISSUE.

EPITHELIUM OF:5.BLOOD VESSELS;

LYMPHATICS.

EPITHELIUM OF:1. PHARYNX,INCLU

DING: ROOT OF TONGUE , AUDITORY TUBE, ETC. TONSILS; THYROID PARATHYROIDS ; THYMUS

2. LARYNX; TRACHEA; LUNGS

3. NERVOUS TISSUE , INCLUDING; HYPOPHYSIS,CHROMAFFIN TISSUE

6. BODY CAVITIES

7.KIDNEY; URETER

8.GONADS; GENITAL DUCTS

9.SUPRARENAL10.JOINT

CAVITIES , ETC

3.DIGESTIVETUBE , INCLUDING : ASSOCIATED GLANDS4.BLADDER5.VAGINA(ALL?),VESTIBULE.6.URETHRA , INCLUDING: ASSOCIATED GLANDS.