ANIMAL REPRODUCTION and DEVELOPMENT Flashcards Preview

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Flashcards in ANIMAL REPRODUCTION and DEVELOPMENT Deck (56):
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Non-animal: Asexual reproduction

Offspring are clones; sexual reproduction's advantage is VARIATION.

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Fission:

Separation of organism into two new cells(amoeba)

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Budding:

New individual splits off from existing one (hydra)

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Fragmentation + Regeneration:

Single parent breaks into parts that regenerate into new individuals (sponge, planaria, starfish)

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Parthenogenesis:

Development of egg w/out fertilization; resulting adult is haploid (honeybees, some lizards)

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HUMAN REPRODUCTIVE ANATOMY

Gonads-
Male-
Female-

Gonads- Reproductive structure responsible for production of gametes.
Male = testis
Female = Ovaries
-Secondary sex characteristics: Indication of sexual maturity but not specifically involved in reproduction (e.g. breasts)

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HUMAN REPRODUCTIVE ANATOMY
1. Female reproduction System:
A.Ovary
B. Oviduct
C. Uterus
*Endometrium
D. Vagina
*Cervix

A)Ovary - OVA, or eggs, are produced. Each female has two ovaries.

B)Oviduct- Eggs move from ovary to uterus through oviduct(fallopian/uterine tube). There are two oviducts, one for each ovary.

C) Uterus - A fertilized ovum implants(attaches) on the inside wall, or the ENDOMETRIUM, of the uterus. Development of the embryo occurs here until birth.

D)Vagina = at birth, the fetus passes through the CERVIX(an opening in the uterus), through the vagina, and out of the body.

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HUMAN REPRODUCTIVE ANATOMY

2. Male Reproductive System
*Testis
-seminiferous tubules, interstitial cells, scrotum
*Epididymis
*Vas Deferens

Testis = Each of the two testes consists of SEMINIFEROUS TUBULES for the production of sperm and INTERSTITIAL CELLS which produce male sex hormones(testosterone and other androgens). The two testes are contained in a single sac, the SCROTUM, which hangs outside the body.

EPIDIDYMIS = This coiled tube, one attached to each testis, is the site for final maturation and storage of the sperm.

VAS DEFERENS = Transfer sperms from one epididymis to urethra.

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HUMAN REPRODUCTIVE ANATOMY

2. Male Reproductive System
*Seminal vesicles
*Prostate gland
* Bulbourethral glands(aka Cowper's glands)
* Penis
-semen

*Seminal vesicles = Two glands, during ejaculation secrete into vas deferens: they make up most of the content for semen.
*Prostate gland = Secretes milky alkaline fluid into urethra. Makes up 30% of semen fluid.

* Bulbourethral glands(aka Cowper's glands) = helps neutralize any urinary acids in the urethra. Protects the sperm.

* Penis = The urethra passes through the penis and serves to transport SEMEN, the fluid containing sperm and secretions, into the vagina. It also serves in the transport of urine out of the body.

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HUMAN REPRODUCTIVE ANATOMY

2. Male Reproductive System - Sperm
Sperm - what is it?
PArts of the sperm -

Sperm = compact packages of DNA specialized for the effective delivery of the male genome. They consists of the following structures:

SPERM HEAD - The head of the sperm contains the haploid nucleus with 23 chromosomes(in humans. At the tip of the sperm head is the ACROSOME(a lysosome containing enzymes which are used to penetrate the egg). The ACROSOME originates from Golgi body vesicles that fuse to form a single lysosome.

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HUMAN REPRODUCTIVE ANATOMY

2. Male Reproductive System -

SEVEnUP:

Seminiferous tubules ---> epidydmis ----> Vas Deferens ---> Ejaculatory Duct ----> Urethra ----> Penis

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GAMETOGENEIS IN HUMANS:

Gametogenesis:

Gametogenesis: Consists of the meiotic cell divisions that produce eggs in females (oogenesis) and sperm in males (spermatogenesis)
-Egg contains most of the cytoplasm, RNA, organelles, and nutrients made by developing embryo.

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GAMETOGENEIS IN HUMANS:

Oogenesis:
*Oogonia
*Primary oocytes
*Follicle
* Secondary Oocyte
*Polar body

Oogenesis: being during embryonic development; OOGONIA(fetal cells) ---->(mitosis) PRIMARY OOCYTES ----> (meiosis begins) and remain at Prophase I until puberty, at which time one primary oocyte during menstrual cycle (averaging 28 days) continues its development through the remainder of meiosis I within the FOLLICLE(which protects and nourishes oocyte) ---> (completion of Meiosis I) SECONDARY OOCYTE(most of cytoplasm) +POLAR BODY(small cytoplasm; may or may not divide but products disintegrate) formed; now arrested at metaphase of meiosis II until----> ovulation.

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GAMETOGENEIS IN HUMANS:

-Ovulation:

Ovulation: releases SECONDARY OOCYTE from the follicle. If fertilized by sperm ---> it moves through the oviduct, the secondary oocyte will begin meiosis II and produce an egg that combines with the chromosomes contributed by the sperm. The secondary daughter cell of meiosis II, again a POLAR BODY(degenerate)

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GAMETOGENEIS IN HUMANS:

-SPERMATOGENESIS:
*Spermatogonia
*Primary Spermatocytes
*Secondary Spermatocytes (how many?)
* Spermatids (how many?)

Spermatogenesis = Begins at puberty within seminiferous tubules of testes. SPERMATOGONIA cells ----> (mitosis) PRIMARY SPERMATOCYTES --->(meiosis) 2 SECONDARY SPERMATOCYTES ----> (Meiosis II) 4 SPERMATIDS.

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GAMETOGENEIS IN HUMANS:

-Sertoli Cells
*spermatozoa(sperm)

-Sertoli Cells: Happens in the seminiferous tubules which provide nourishment to spermatids as they differentiate into mature SPERMATOZOA (sperm. They complete maturation(gain motility and are stored) in the epididymis.

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Capacitation:

Penultimate(last but one in a series of things) step in maturation of the spermatozoa while in the vagina, allows for egg penetration.

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HORMONAL CONTROL OF HUMAN REPRODUCTION
1. Female Reproductive Cycle
What 2 cycles do they consist of?

1. OVARIAN CYCLE(ovary)
2. MENSTRUAL CYCLE (uterus)

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HORMONAL CONTROL OF HUMAN REPRODUCTION
1. Female Reproductive Cycle
-Menstrual Cycle: What is it divided into?
What is the process like?
-HYPOTHALAMUS AND ANTERIOR PITUITARY INITIATE
-FOLLICLE DEVELOPS
-DEVELOPMENT OF ENDOMETRIUM

It is divided into follicular, ovulation, luteal, menstruation(proliferative/secretory/menstruation)

HYPOTHALAMUS AND ANTERIOR PITUITARY INITIATE: monitor estrogen and progesterone in blood;
Low level ---> hypothalamus -----> GnRH ---->FSH and LH(via anterior pituitary- NEGATIVE FEEDBACK------>
FOLLICLE DEVELOPS ------> FSH stimulate follicle to secrete estrogen----> lots of estrogen(positive feedback on AP)-----> LH SURGE ----> OVULATION(follicle is now CORPUS LUTEUM-maintained by LH[which along w/ estrogen begins to decrease after ovulation], secretes -----> estrogen + progesterone -------> DEVELOPMENT OF ENDOMETRIUM(thickens in prep for implantation of fertilized egg)

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HORMONAL CONTROL OF HUMAN REPRODUCTION
1. Female Reproductive Cycle
-Menstrual Cycle:
IF IMPLANTATION OCCURS ----->
*Corpus Luteum

IF IMPLANTATION OCCURS -----> embryo (placenta) secretes chorionic gonadotropin(HCG) ---> mainting CORPUS LUTEUM----> PRODUCTION of E+P remain high -----> endometrium stays -----> HCG is later replaced by progesterone from placenta.

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HORMONAL CONTROL OF HUMAN REPRODUCTION
The Menstrual Cycle: Consists of the thickening of the endometrium of the uterus in preparation for implantation of a fertilized egg and the shedding of the endometrium if plantation does not occur.

OVARIAN CYCLE
1. Follicular Phase:
2. Ovulation:
3. Luteal Phase:
*Estrogen
*Progesterone
* Corpus Luteum

OVARIAN CYCLE

1. Follicular Phase = development of egg and secretion of estrogen from follicle.
2. Ovulation: Midcycle release of egg.
3. Luteal Phase = Secretion of ESTROGEN and PROGESTERONE from CORPUS LUTEUM after ovulation.

Estrogen- thicken endometrium
Progesterone - development and maintenance of endometrial wall.

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HORMONAL CONTROL OF HUMAN REPRODUCTION

2. Male Reproductive Cycle:
-The hormonal process
*Sertoli

GnRH ---> FSH + LH(also called ICSH, interstitial cell stimulating hormone -----> testosterone and androgens from testis_
- FSH and testosterone -----> influence SERTOLI cells to promote development of sperms (nourish sperm during development - spermatogenesis). Hormone and gamete production are constant unlike female.

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EMBRYONIC DEVELOPMENT
-Four stages in growth and development of animal:

-Gametogenesis (sperm/egg formation)
-Embryonic Development (fertilization of egg until birth)
-Reproductive maturity(puberty)
- aging process to death.

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EMBRYONIC DEVELOPMENT
- In mammals, development is 2 stages: What are they?
*Fetus

-Embryonic followed by fetal development.
-FETUS is an embryo that resembles the infant form.

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development(sea urchin-echinoderm)

*Fertilization-
1)Recognition
*Vitelline Layer
* Zone pellucida
2) Penetration
3) Formation of fertilization membrane.
4) Completion of meiosis II in the secondary oocyte:
5) Fusion of nuclei and replication of DNA.

Fertilization - Sperm penetrates the plasma membrane of the secondary oocyte.

1)Recognition: Before penetration can occur, the sperm secretes a protein that binds with special receptor molecules that reside on a glycoprotein layer surrounding the plasma membrane of the oocyte. This VITELLINE LAYER(or ZONA PELLUCIDA in humans) insures that fertilization occurs only between egg and sperm of the same species.

2)Penetration = plasma membranes of sperm and oocyte fuse, sperm nucleus enter oocyte.

3)FORMATION OF THE FERTILIZATION MEMBRANE= The vitelline layer forms a fertilization membrane which blocks the entrance of additional sperm.

4)COMPLETION OF MEIOSIS II IN THE SECONDARY OOCYTE = In humans, sperm penetration triggers meiosis II in the oocyte, producing an ovum(egg) and polar body. The polar body is discharged through the plasma membrane.

5)FUSION OF NUCLEI and REPLICATION OF DNA = The sperm and ovum nuclei fuse, forming a zygote nucleus consisting of 23 pairs of chromosomes (in humans). Each chromosome replicates so that it consists of two identical chromatids.

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development(sea urchin-echinoderm)

B)CLEAVAGE
*blastomers
1.EMBRYO POLARITY- animal pole & vegetal pole,yolk
2. POLAR AND EQUATORIAL CLEAVAGE
3.RADIAL and SPIRAL CLEAVAGES
4. INDETERMINATE and DETERMINATE CLEAVAGES:

CLEAVAGE: Rapid cell divisions without cell growth each cell = BLASTOMERE (less cytoplasm than original zygote)

1. EMBRYO POLARITY: Egg has upper, AMIMAL POLE and lower, VEGETAL POLE. Cells formed at the vegetal pole contain more YOLK, or stored food, because the yolk material. denser than the surrounding cytoplasm, settles to the bottom of the egg.
2. POLAR & EQUATORIAL CLAVAGE = Early cleavages are polar, dividing the egg into segments that stretch from pole to pole(like sections of an orange)
3. RADIA & SPIRAL CLEAVAGES = Radial in deuterostomes forming (indeterminate) cells at animal and vegetal poles that are aligned together, top cells directly above bottom cells. In protostomes (spiral-determinate), cells formed on top are shifted.
4. INDETERMINATE & DETERMINATE CLEAVAGES = indeterminate(blastomeres can individually complete normal development if separated). Determinate cannot develop into complete embryo if separate; each is differentiated into part of the embryo.

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development(sea urchin-echinoderm)

-MORULA

Morula - successive cleavage results in solid ball of cells(~8+cells stage) (first 8 cells are totipotent)

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development(sea urchin-echinoderm)

-Blastula
*Blastocoel
*Blastocyst

BLASTULA - Cell division continues; liquid fills morula and pushes cells out to form circular cavity surrounded by single later of cells. BLASTOCOEL is the cavity(~128 cells stage)

-In humans the blastula is called the BLASTOCYST and implants into the endometrium(development here).

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development(sea urchin-echinoderm)

-Gastrula(tion):

Formation of the gastrula, or GASTRULATION, occurs when a group of cells invaginate(move inward) into the blastula, forming a two-layered embryo with an opening from the outside into a center cavity.

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development(sea urchin-echinoderm)
-Three Germ Layers

Ectoderm, mesoderm, and endoderm(3rd layer if formed b/w outer and inner layer of invaginated embryo).
A)Endoderm - epithelial lining of digestive & respiratory, parts of liver, pancreas, thyroid, & urinary bladder lining.

B) Mesoderm - Musculoskeletal, circulatory system, excretory system, gonads, connective tissue, portions of digestive & respiratory,

C) Ectoderm = Nervous system(brain & spinal cord, integument(epidermis & hair/ epithelium of nose, mouth, anal canal), sense structures, (lens of eye, retina), teeth, neural tube.

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development

-Gastrula - ARCHENTERON

Archenteron - center cavity formed by gastrulation.

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development

-Gastrula - BLASTOPORE

Opening into archenteron, becomes mouth (protostomes) or the anus (deuterostomes).

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development

EXTRAEMBRYONIC MEMBRANE DEVELOPMENT

EXTRAEMBRYONIC MEMBRANE DEVELOPMENT - In birds, reptiles, and humans (called AMNIOTES), this develops as follows

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development

Extraembryonic membrane development - CHORION
*Placenta

CHORION - Outer membrane. Birds & reptiles: membrane for gas exchange. Mammals: chorion implants into endometrium, and later, the chorion and maternal tissue form the PLACENTA (A blend of maternal and embryonic tissues across which gases, nutrients, and wastes are exchanged.)

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development
-Extraembryonic membrane development - ALLANTOIS

ALLANTOIS: Sac that buds off from archenteron( cavity of gastrula forming primitive gut) that eventually encircles the embryo, forming layer below chorion. Birds + reptiles: initially stores waste products as uric acid. Later fuses w. chorion -----> membrane for gas exchange w/ blood vessels below.

Mammals: allantois transports waste products to placenta; eventually forms umbilical cord b/w embryo & embryo and placenta: transporting gases, nutrients, and wastes. Becomes Urinary bladder in adults.

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development
-Extraembryonic membrane development - AMNION
*Amniotic cavity

- A fluid-filled cavity that cushions the developing embryo, much like the coelom cushions internal organs in coelomates.

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EMBRYONIC DEVELOPMENT

- Stages of Embryonic Development
-Extraembryonic membrane development - YOLK SAC

Yolk Sac - In birds & reptiles, yolk sac membrane digests enclosed yolk. Blood vessels transfer nutrients to embryo. In placental mammals, yolk sac is empty, umbilical cord/placenta delivers nutrients.

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DIFFERENCES IN DEVELOPMENT

- External development:

-External development: fish & amphibians have external fertilization in water; reptiles, birds, and some mammals have internal fertilization then lay eggs.

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DIFFERENCES IN DEVELOPMENT

-Non-placental internal development:

Certain animals( e.g. marsupials, tropical fish) w/ no placenta either, limited exchange of food + O2 b/w mother/young.

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DIFFERENCES IN DEVELOPMENT

-Placental internal development:

(e.g.- humans). Major components are umbilical cord & placenta system: O2 received direct from mother (fetal lungs not fxnal fluid as shock absorber; placenta formation begins w chorion; blood cessels of allantois wall enlarge and become umbilical vessels.

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ORGANOGENESIS-

Cells continue to divide after gastrulation ----> differentiate ---> develop into specific tissues & organs. The following organs is characteristic of the chordates.

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ORGANOGENESIS-

*Notochord-

*Notochord: Cells along dorsal surface of mesoderm layer form notochord, a stiff rod that provides support in lower chordates. Vertebrae of higher chordates are formed from nearby cells in mesoderm.

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ORGANOGENESIS-

*Neural Tube =
-neural groove
- Neural Crest

Neural Tube : In ectoderm later directly above notochord, layer of cells forms neural plate. Plate indents, forming NEURAL GROOVE, then rolls up into a cylinder, the NEURAL TUBE. This develops into the CNS. Additional cells roll off top of neural tube and form NEURAL CREST(which form teeth, bones, muscles of skull, pigment cells in skin, and nerve tissue)

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Notable exceptions to the general embryonic development patterns

1) Frog
*Gray crescent

*Gray crescent = When the sperm penetrates a frog egg,----> a reorganization of the cytoplasm results in the appearance of a gray, crescent-shaped region, called the gray crescent.

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Notable exceptions to the general embryonic development patterns

1) Frog
*Gastrulation
-Dorsal Lip.

Gastrulation - During gastrulation, cells migrate over the top edge of the blastopore. The top edge, called the DORSAL LIP, forms from the same region earlier occupied by the gray crescent. The bottom and sides of the blastopore edge are called the ventral lip and lateral lips, respectively.

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Notable exceptions to the general embryonic development patterns

1) Frog
*Yolk-

Yolk: The yolk material is much more extensive in the frog than in the sea urchin. Cells from the vegetal pole rich in yolk material form a YOLK PLUG near the dorsal lip.

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Notable exceptions to the general embryonic development patterns

2. Bird
-Blastodisc

BLASTODIC: Yolk of bird egg is very large, not involved in cleavages; cleavages only occur in blastula that consists of flattened, disk-shaped region that sits on top of yolk(BLASTODISC)

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Notable exceptions to the general embryonic development patterns

2. Bird
-Primitive Streak:

Primitive Streak: When gastrulation begins, invagination occurs along a line called the primitive streak. As cells migrate into the primitive streak, the crevice formed becomes an elongated blastopore (rather than a circular blastopore, as found in sea urchins and frogs)

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Notable exceptions to the general embryonic development patterns

3. Humans and most other mammals
-Blastocyst:
*Trophoblast
*Embryonic Disc

Blastocyst: Blastula stage consists of 2 parts - an outer ring of cells, the TROPHOBLAST, and an inner mass of cells, the EMBRYONIC DISC.

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Notable exceptions to the general embryonic development patterns

3. Humans and most other mammals
Trophoblast:

Trophoblast: The outer ring of cells, or trophoblast, serves several functions.
-It produces HUMAN CHORIONIC GONADOTROPIN (HCG) to maintain e+p production from CORPUS LUTEUM(which in turn maintains endometrium); it later forms the CHORION (later forms PLACENTA)

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Notable exceptions to the general embryonic development patterns

3. Humans and most other mammals
-Embryonic disc:

Within the cavity created by the trophoblast, a bundle of cells called the INNER CELL MASS (ICM) clusters at one pole and flatten into embryonic disc(analogous to blastodisc of birds and reptiles). Primitive Streak develops ----> gastrulation ----> development of embryo + extraembryonic membranes (except chorion)

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FACTORS THAT INFLUENCE DEVELOPMENT

1. Influence of egg cytoplasm

Cytoplasmic material is distributed unequally in the egg. The gray crescent in frogs and the yolk in bird eggs are examples. When cleavages divide the egg, the quality of cytoplasmic substances will vary among the daughter cells.

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FACTORS THAT INFLUENCE DEVELOPMENT

2. EMBRYONIC INDUCTION:

Influence of one cell/group of cells over neighboring cells; ORGANIZERS (controller cells) secrete chemicals that diffuse among neighboring cells, influence their development.
2nd dorsal lip ----->becomes an embryo.

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FACTORS THAT INFLUENCE DEVELOPMENT

3. HOMEOTIC GENES: Control of development by turning on and off other genes that code for substances that directly

- Control of development by turning on and off other genes that code for substances that directly affect development.
Mutant homeotic genes in fruit flies ----> wrong body parts in wrong places.

HOMEOBOX - identifies a particular class of genes that control development.

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FACTORS THAT INFLUENCE DEVELOPMENT

4.APOPTOSIS:

Apoptosis: Programmed cell death that is a part of normal cell development. Essential for development of nervous system, operation of immune system, and destroy tissue(webbing) b/w fingers/toes.

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Amniotes:

Group of tetrapods (four-limbed animals w backbones or spinal columns) that have a terrestrially adapted egg; supported by several extraembryonic membranes.