Chapter 27 Lecture - Mitosis & Meiosis

Mitosis occurs in what type of cells?

somatic cells

Are cells genetically identical daughter cells during mitosis?

yes

Each cell that goes through mitosis finishes with?

2 diploid daughter cells, each with 46 chromosomes

What stage occurs before mitosis?

interphase

What occurs during prophase?

Chromosomes condense, nuclear envelope breaks down, and spindle fibers begin to form.

What occurs during metaphase?

chromosomes align at the metaphase plate

What occurs during anaphase?

sister chromatids separate and move to opposite poles of the cell

What occurs during telophase?

Chromosomes decondense, nuclear envelopes reform around the two sets of chromosomes, and the cell prepares for cytokinesis.

What is a zygote?

a fertilized egg

What division does a zygote go under?

mitosis

ovaries and testes produce what kind of gametes?

haploid

How many cells come from one round of meiosis?

4 haploid daughter cells (each 23 chromosomes)

Why are gamete cells haploid?

to unite with another gamete to create a 46 chromosome cell

are meiosis cells unique?

yes

Prophase I

mitotic spindle forms and crossover occurs

What is crossover?

exchange of genetic material between homologous chromosomes

Metaphase 1

homologous chromosomes align at the metaphase plate

Are homologous chromosomes identical at the metaphase state?

no

Anaphase 1

homologous chromosomes separate, and chromosomes begin to move toward opposite poles

Telophase 1

Chromosomes arrive at the poles with each chromosome consisting of 2 non-identical sister chromatids

cytokinesis

cytoplasm divides and 2 haploid daughter cells are formed

Prophase 2

mitotic spindle forms

Metaphase 2

chromosomes align at the metaphase plate

Anaphase 2

sister chromatids separate and move as un-replicated chromosomes toward opposite poles

Telophase 2

chromosomes arrive at opposite poles and begin forming haploid daughter cells

Cytokinesis (II)

cytoplasm divides and results in 4 haploid, unique daughter cells

What are the primary sex organs?

testes and ovaries

What do primary sex organs produce?

gametes (sperm and ova)

What would the chromosomes of a male look like?

XY

What would the chromosomes of a female look like?

XX

Where are the testes located?

within the scrotum

What is the function of the seminiferous tubules?

site of sperm production

What does the spermatic cord do?

connects the testes to the rest of the body

What is enclosed inside the spermatic cord?

vas deferens, nerve fibers, blood vessels, and lymphatics

What is the pathway for sperm?

1. seminiferous tubules

2. rete testis

3. efferent duct

4. epididymis head

5. epididymis body

6. epididymis tail

   • where sperm is stored until ejaculation

What occurs in the epididymis?

sperm mature and mature sperm will enter into the vas deferens upon ejaculation

Vas deferens

muscular tube that transports and stores sperm

What structure is cut during a vasectomy?

vas deferens

What do the seminal vesicles do?

secretes an alkaline/yellow substance that is vicious. helps to neutralize any acidity from the urine that my be left over in the urethra.

ejaculatory ducts

enters the prostate and transports sperm to urethra

Prostate

secrete a milky, slightly acidic, citrate to activate sperm

Bulbourethral gland

secretes a clear, viscous substance to lubricate the glans penis (tip of the penis)

Urethra

both urinary and reproductive

Erection

parasympathetic response

blood vessels dilate

Ejaculation

sympathetic response

smooth muscle contract propels semen

Type A spermatogonia

stem cells; undergoes mitosis and creates 2 daughter cells

Type B spermatogonia

stem cells; undergoes mitosis and creates the primary spermatocyte

Primary spermatocyte

goes through one round of meiosis and creates 2 daughter cells(diploid turning into haploid)

Secondary spermatocytes (haploid)

both daughter cells undergo meiosis II and resulting in 4 haploid cells

Spermatids

the result of meiosis II from the secondary spermatocytes

Spermiogenesis

The last step; when spermatids elongate and form tails, takes 24 days

spermatogenesis

sperm production that occurs in the seminiferous tubules of testis

After 25 days of spermatids forming, what final form do they take?

spermatozoons (sperm)

Spermatozoons (sperm) consist of what?

• Head

  • Acrosome

• Midpiece

• Tail

The head of the sperm contains what?

nucleus containing DNA

What is the function of the acrosome

covers the top of the head; contains enzymes that enable the sperm to penetrate the egg

What does the midpiece contain?

the mitochondria

What happens to testosterone during puberty?

levels rise and sperm production begins

What happens to testosterone during adulthood?

It’s stable and is at maximum testosterone and sperm production

What happens to testosterone during older adulthood?

levels and sperm production decline

GnRH from the hypothalamus stimulates the anterior pituitary gland to secrete what?

FSH & LH

FSH stimulates nurse cells to secrete what?

androgen-binding protein (ABP)

LH stimulates interstitial cells to secrete what?

testosterone

In the presence of androgen-binding protein, testosterone stimulates what?

spermatogenesis

What does the negative feedback of testosterone do?

reduce GnRH secretion and pituitary sensitivity to GnRH

What can nurse cells secrete?

inhibin

What does the inhibin secretion of nurse cells do?

reduces sperm production without reducing testosterone secretion