Reproduction and Development

Asexual Reproduction

• Def

A organism that produces genetically identical offspring

Types of Asexual Reproduction

• Binary Fission

• Budding

• Regeneration

• Parthenogenesis

Binary Fission

• Examples

• How does it work

• Binary Fission

  • DNA replicates

  • Septum forms in the middle and splits the organism in two

EX: Prokaryotes, Mitochondria

Budding

• Examples

• How does it work

• Budding

  • DNA replicated and deposited into bud which forms into a new organism

EX: Hydra, Yeast

Regeneration

• Piece of organism breaks off, can regenerate broken segment.

EX: Hydra, Planaria, Fungi

Parthenogeneis

Unfertilized egg can develop into a viable organism.

Honeybees exhibit haplodiploidy (males are haploid, and females are diploid)

Sexual Reproduction

• What does it entail?

• What kind of offspring is created genetically?

Gametes (male sperm and female egg) combine to form genetically distinct offspring

Germ Cells

• What are they

• How are they different throughout organisms

They are cells that produce gametes via meiosis

• The opposite of somatic cells.

Spermatogenesis

Formation of haploid spermatozoa (sperm cells) from diploid germ cells (spermatogonia)

Spermiogenesis

Final Stage of Spermatogenesis

• Spermatid differentiates into spermatozoa

Sperm Structure

• What are the main parts of the sperm

• Head

• Midpiece

• Tail

What is the head of the sperm for?

• Head: Nucleus and acrosome

What is the midpiece of the sperm for?

Mitochondria (ATP production)

What is the tail of the sperm for?

Flagellum for motility.

Sperm Pathway Mneumonic

SEVEn UP

• Semiferous Tubules

• Epididymis

• Vas Deferens

• Ejaculatory Duct

• Urethra

• Penis

Semiferous Tubules

• What occurs here

• What is at the location

Site of Spermatogenesis

Contain Sertoli cells.

Epiddiymis

Maturation and storage of sperm.

Vas Deferens

Ejaculatory Duct

Urethra

Leads sperm to ejaculation out of penis.

Penis

the outer extremity that removes sperm. Ac

Accessory Glands of the male anatomy

• Seminal Vesicles

• Prostate Gland

• Bulbourethral Glands

Where are the accesory glands that feed into the sperm pathway located?

Ejaculatory Duct

What do seminal vesicles secrete?

1. Fructose

2. Viscous Mucus (cleans and lubricates urethra)

3. Prostaglandins (stimulate urethral contraction)

What do bulbourethral glands secrete?

Viscous mucus

What do Prostate glands secrete

Alkaline secretions to counteract uterine acidity.

Sertoli Cells

Nourish sperm cells

Hormones in males

• Main 2

Lutenizing Hormones

Follicle Stimulating Hormones

What does Follicle stimulating hormone (FSH) do?

• What does it affect?

Stimulates sperm production in seminiferous tubules.

• It activates Sertoli (FSH) cells

• Have a negative feedback loop on FSH, by releasing inhibin

What does Lutenizing Hormone Do?

Stimulates Leydig Cells.

This helps produce testosterone.

What does Testosterone do?

Helps with sperm maturation and male secondary sex characteristics.

What is the ovary

Ovary: Produces egg cells

Fimbriae:

Receives Eggs released from ovary

What is the Oviduct / Fallopian tube

Path between ovaries and uterus

What is the uterus used for?

Provides ideal environment for fertilized egg to implant and develop

What are the layers of the uterus

● Perimetrium (outer)

● Myometrium (middle, muscular)

● Endometrium (inner epithelial)

What is the myometrium made of, what layer is it?

Middle layer, muscular

What is the endometrium made of?

Endometrium (inner epithelial), is also the inner part.

What is the purpose of the Cervix

Narrow opening between the uterus and the vagina.

What is the purpose of the vagina?

opening to external environment, where sperm can enter and birth occurs

Oogenesis

Embryo

• Starts with primordial germ cell

• Turns into an oogonium (2n)

• Undergoes mitotic divisions

Birth

• Primary Oocyte (2n)

• Cell is arrested in prophase I

Puberty:

• Undergoes meiosis I and completes it, start of Meiosis II

• creates first polar body

• We start a secondary oocyte.

• We arrest in metaphase II.

Fertilization

• Ovulation sperm entry sees the completion of meiosis II

• Creation of a second polar body

Then you create a fertilized egg.

Hormones in Females

• Lutenizing Hormone

• Follicle Stimulating Hormone

• Estrogen and Progesterone

Follicle Stimulating hormone in women

Stimulates follicles in the ovary to develop, as well as estrogen and progesterone production

What is a follicle (women)

● Follicle: Fluid filled sac containing immature egg (arrested in

prophase I); upon ovulation, transforms into corpus luteum

The little sac with the egg in it, this will turn into the corpus luteum upon rupture.

Lutenizing Hormone

Stimulates ovulation of egg, corpus luteum formation

Estrogen and Progesterone in women

Menstrual cycle and reproduction. These also are in charge of secondary sex characteristics.

Hormone Feedback Loops (positive and negative)

• Examples of each

Positive feedback loops stimulate biologic pathways

• Lactation

• Childbirth

Negative feedback loops inhibit biologic pathways

• Menstrual Cycle

Lactation

• Infant suckling increases prolactin, which stimulates milk production (lactation)

• Oxytocin is also produced, which releases milk (milk let down reflex)

Childbirth (as a feedback loop)

• Oxytocin induces contractions that initiate childbirth; when baby’s head pushes against cervix, it stimulates the hypothalamus and pituitary to release more oxytocin

Menstrual Cycle

Menstrual Cycle

• Hypothalamus releases gonadotropin releasing hormone (GnRH)

• GnRH acts on anterior pituitary gland to release FSH and LH

• FSH and LH act on ovaries to release estrogen and progesterone

• Estrogen and progesterone exhibit negative feedback on pituitary gland and hypothalamus

Ovulation meaning

Egg is released from the graafian follicle

• Fimbriae receive egg, cilia sweep egg travels through oviduct awaiting fertilization.

Luteal Phase

• Follicle develops into corpus luteum

• Corpus luteum releases progesterone and some estrogen, and is maintained by FSH and LH

• Estrogen and progesterone exhibit negative feedback

Steps of the menstrual cycle

1. LH and FSH promote follicle growth. The growing follicle secretes increasing amount of estrogen.

• Estrogen leads to the thickening of the endometrium

2. Increased estrogen causes LH to surge

3. LH spike triggers ovulation

4. Corpus Luteum secretes progesterone and estrogen, which causes the thickening of the endometrium.

• Causes the luteal phase

5. The corpus Luteum dissolves and hormone levels decrease leading to menstruation.

What happens if implantation does not occur.

FSH and LH decrease until corpus luteum can no longer be maintained

• Estrogen and progesterone drops

• Endometrium sloughs off (menstruation), cycle repeats

If implantation occurs

• Outer layer of placenta produces human chorionic gonadotropin (hCG), which aids in maintaining corpus luteum

• Progesterone and estrogen levels maintained, endometrium thickens (no menstruation)

Human Choroinic Gonadotropin (hCG)

Aids in maintaining corpus luteum when it is implanted.

Progesterone and estrogen levels become maintained, and the endometrium thickens. (no menstruation)

Fertilization

• Meaning

The joining of a haploid sperm and haploid egg cell to form a diploid zygote

Capacitation

The final maturation step for sperm prior to encountering the egg, triggered by secretions from the uterine wall

• Destabilizes plasma membrane proteins and lipids:

• Prepare sperm tip for acrosomal reaction

• Increased calcium permeability resulting in a hyperactive state

MORE CALCIUM MEANS MORE FAST YIPEE

Corona Radiata

Outermost layer, nourishes the developing egg

Vitelline Layer

Layer of glycoproteins (jelly coat) above the plasma membrane.

• Named the zona pellucida in mammals.

Acrosomal Reaction

1. Sperm break through corona radiata to approach zona pellucida

2. Sperm actin recognizes zona pellucida ZP3 protein (same-species fertilization), triggering acrosomal reaction:

• Releases hydrolytic enzymes, breaking down zona pellucida’s glycoprotein membrane to access plasma membrane

3. Sperm and egg plasma membranes fuse, genetic material combines

Total Sperm and Egg binding reaction + Polyspermy blocks

1. Sperm head makes contact

2. Acrosomal Reaction occurs, allowing sperm to penetrate into the viteline membrane

3. Fast Block of polyspermy: Sperm and egg plasma membranes fuse, leading to a temporariy depolarization which blocks sperm from entering. (Na+ influx)

4. Sperm nucleus enters the egg

5. Slow Block of Polyspermy: egg releases cortical granules, dethatching the plasma membrane from the vitelline membrane.

6. Cortical reaction leads to the formation of impenetrable fertilization envelope.

How does the formation of twins work: Monozygotic

A sperm and an egg are fertilized, and once fertilized, the zygote splits into two, causing identical genetic material.

How does the formation of twins work: Dizygotic

Two different eggs are fertilized, which causes twins with different genetic material

What is cleavage

• What does it result in?

Rapid cell divisions without changing the total mass of cells

Resulting cells = blastomeres

What are cleavages categorized on?

Axis of cleavage

Fate of cells

Evenness of embryo division

Spiral Cleavage

• what does it look like

• Examples of cells

Cells that deviate from the axis.

• EX: Protostomes

Radial Cleavage

• what does it look like

• Examples of cells

Cells aligned in vertical axis (ex: deuterostomes)

Regulative fate of a cell.

• what does that mean for it’s fate?

• Example

(Indeterminate)

blastomeres are totipotent, do not have pre-determined fate (ex: deuterostomes)

Mosaic fate of a cell

• what does that mean for it’s fate?

• Example

Mosaic (determinate): blastomeres have decided fate (ex: protostomes)

Evenness of Embryo division:

• What are the types?

Can be Holoblastic Cleavage

or

Can be Meroblastic cleavage

Holoblastic Cleavage

• What undergoes it, and what is the distribution of materials inside?

Even cleavage with little yolk

• Non egg laying species (humans)

Meroblastic cleavage

Uneven cleavage that forms the animal and vegetal pole.

• Egg laying species (not frogs)

Animal Pole

• High rate of cleavage

• Little yolk

Vegetal Pole

• Low rate of Cleavage

• Lots of yolk

Morula

Ball of blastomeres

16-32

Blastula

Cell mass that has a hole.

Formation of blastocoel, a hollow fluid filled center

Blastocyst

Blastula cells differentiate to form blastocyst which implants into the uterine wall.

Blastocyst Implantation

As embryo reaches the uterus, blastula differentiates to form a blastocyst that implants into the uterine wall

What is the gastrula?

What are it’s parts?

Formation of the trilaminar embryo

3 germ layers: Endoderm, mesoderm, ectoderm

What is the blastopore?

• What does it develop into

Cells in the gastrula that invaginate to form blastopore, which will develop into gut tube (archenteron) that forms eventual digestive tract

Ectoderm gives rise to what?

• Nervous system

• Sensory parts of ear, eye, nose

• Epidermis of skin, hair and nails

• Mammary and sweat glands

• Pigmentation cells

• Enamel of teeth

• Adrenal medulla

Attract-oderm

Want to look good, good appearances.

Mesoderm forms what?

• Bones and skeleton

• Muscles

• Cardiovascular system

• Gonads

• Adrenal Cortex

• Spleen

• Notochord (induces spinal cord formation from ectoderm)

Means-oderm

Endoderm forms what?

• Epithelial lining of digestive, respiratory and excretory systems

• PLTT (pancreas, liver, thyroid/parathyroid, thymus)

What are stem cells?

Undifferentiated Cells that have the potential to develop into different things.

Totipotent cells

Stem cells capable of developing into a complete embryo or any cell type

Pluripotent cells

Stem cells that can differentiate into any of the 3 germ layers

Multipotent cells

Stem cells that can differentiate into any cell type within a particular lineage.

• Endoderm

• Mesoderm

• Ectoderm

Differentiated cells

Cells that are fully specialized and can only reproduce cells of their own type

Nuerula

Neurula: Term for embryo when it develops the nervous system

Neurulation Process

• 3 main steps

1. Notochord (derived from mesoderm) stimulates ectoderm to thicken into neural plate

2. Neural plate folds to form neural tube

• Some cells migrate off neural crest and contribute to tooth, craniofacial, skin pigmentation

3. Neural tube differentiates into CNS, while mesoderm cells (somites) eventually form vertebrae and skeletal muscles associated with axial skeleton

Extraembryonic Development

• Def

Structures outside of the embryo that provide protection and nourishment to fetus

Amnion meaning

• What has it?

• What do not?

Innermost layer which secretes amnionic fluid. It cushion embryo

Amniotes

• What animals represent this

have amnion (reptiles, mammals, birds)

• reptiles, mammals birds

Anamniotes

• What animals represent this

Lack amnion

• (amphibians, fish)

Choiron

Outermost protective layer

Placental Mammals: Choroin

Forms fetal half of placenta (nutrient exchange)

Egg laying mamals: Choroin

Membrane for gas exchange underneath egg shell.

membrane for gas exchange underneath egg shell

Allantois

Allantois: Sac buds off archenteron, stores waste for disposal

• Placental mammals: transports waste to placenta, forms umbilical cord and eventually urinary bladder in adults

• Egg-laying mammals: stores uric waste, later fuses with chorion to aid in gas exchange

Yolk Sac

• Placental mammals

• Egg - laying animals

Yolk sac:

• Placental mammals: Does not contain yolk. Functions temporarily until the placenta forms, providing early nutrients and serving as the first site of blood cell formation.

• Egg-laying animals: Contains yolk, supplies all necessary nutrients to the developing embryo.

Factors that influence development (4)

• Embryonic Induction

• Homeotic genes

• Apoptosis

• Temperature dependent sex determination