Chapter 27 - the reproductive system

Four processes that allow the production of offspring

1.) Gamete formation

2.) Copulation

3.) Fertilization

4.) Gestation and parturition

Gamete formation

Sperm and ova (egg)

Copulation

Sperm and egg must be brought together

Fertilization

Combining genetic content of the sperm and the egg

Gestation and parturition

Development and birth of the fetus

Meiosis

Nuclear division that occurs only in the gonads and results in the formation of gametes

Importance of meiosis

-Why are these important for meiosis?

1.) Reduces the number of chromosomes in gametes by one half

2.) Produces genetic variability

*1.) important for abnormalities and termination of embryo

*2.) Produces genetically variable gametes for species survival

Before meiosis begins, what happens to chromosomes

Chromosomes in diploid (2n) parent cell replicate

What are replicated chromosomes called

Sister chromatids

Diploid (2n)

Containing two complete sets of chromosomes (almost all body cells) in humans —> 46 chromosomes

Haploid (n)

Containing a single set of unpaired chromosomes (eg. sperm + ovum) in humans —> 23 chromsomes

Homologous chromsomes

Matched pairs of chromosomes containing genetic information

-One chromosome is inherited from one parent, the second chromosome from the other parent —> this creates the diploid number

In meiosis, homologous chromosomes will...

Synapse to form tetrads

Meiosis I

1.) Crossing over occurs

2.) Tetrads align randomly

3.) Homologous chromosomes separate and move to opposite poles

4.) Cleavage occurs

Crossing over

Exchange of genetic material (genetic variability)

What does not happen when homologous chromsoms separate and move to opposite poles

Sister chromatids do NOT separate here

Result of cleavage

Produces 2 daughter cells haploid in nature (1/2 genetic info)

What is the result of meiosis I?

Daughter (haploid) enter meiosis II

Meiosis II steps

1.) Formation of new spindle

2.) Chromosomes line up at equator

3.) Sister chromatids separate and move to opposite poles

4.) Cleavage occurs

What is the result of meiosis II?

4 haploid daughter cells

Hypothalamic Pituitary Gonadal (HPG) axis

the interaction of hormones released by the hypothalamus, anterior pituitary, and gonads

What is the function of the HPG axis

Regulate gonadal hormone release, gamete formation, and reproductive oxygen function

Important structures in HPG axis

1.) Hypothalamus

2.) Anterior pituitary gland

3.) Gonads

Hypothalamus function

Releases gonadotropin-releasing hormone (GnRH)

Anterior pituitary gland

Releases follicle-stimulating hormone (FSH) and lutenizing hormone (LH) in response to GnRH presence

Gonads

release sex hormones and produce gametes in response to LH and FSH

Testes

Male gonads enclosed and protected by scrotum

What are the testes and scrotum composed of

Skin and superficial fascia

Importance of scrotum

Allows testes to be 3 degrees lower than internal body temperature for optimal lower temp. sperm production

What allows testes to maintain optimal temperature?

Musculature

1.) Dartos muscle

2.) Cremaster muscle

Dartos muscle

Changes surface area of scrotal tissue

-Decreases in surface area (contraction) will decrease heat loss

Cremaster muscle

Changes position of testes

a.) elevation through contraction to hold heat

b.) Depression (colder)

Characteristics of the testes

1.) Vasculature

2.) Innervation

Vasculature of the testes

1.) Testicular arteries supply each testis

2.) Testicular veins drain testes

Innervation of testes

Sympathetic and parasympathetic divisions serve each testis

Structures of testes

-What do they form?

1.) Nerve fibers

2.) Blood vessels

3.) Ductus deferens

4.) Lymphatics

Form spermatic cord

Seminiferous tubules function

Location of sperm production

What happens to immature sperm in seminiferous tubules

Move through rete testis to epididymis

Testicular cancer

Formation of malignant tumor in one or both testes

-Can be seminoma or non-seminoma

Symptoms of testicular cancer

Painless lump or swelling of testis, dull pain in lower pelvis and/or lower back S

Seminoma

Most frequently seen

-least threatening (cancer cells less aggressive in growth)

Non-seminoma

More dangerous

-Cancer cells divide faster

Testicular cancer is caused by…

Genetics and family history, Klinefelter syndrome, persistent/chronic inflammation

Treatment of testicular cancer

Chemotherapy and radiation, surgery

Accessory ducts to testes

1.) Epididymis

2.) Ductus deferens

3.) Urethra

Epididymis

Stores immature sperm

-As sperm travel through duct, develops ability yo swim W

What happens to sperm that do not leave the epididymis

Starts behaving oddly where they cannot fertilize eggs —> phagocytized and destroyed

Ductus deferens (vas deferens)

Transports sperm out of epididymis during ejaculation

Ductus deferens ends at…

Ampula

Ampulla ends where?

At ejaculatroy duct

Ejaculatory duct empties into…

The urethra

Vasctomy

Ductus deferens cut or cauterized

Urethra

Terminal portion of male duct system

Three divisions of urethra

1.) Prostatic urethra

2.) Intermediate part

3.) spongy urethra

Prostatic urethra

Portion surrounded by prostate glandI

Intermediate part

Connects prostatic urethra to spongy urethra

Spongy urethra

Runs through penis and opens to exterior of body

Penis function

Deliver sperm to female reproductive tract during copulation

Penis ends in

Glans

Glans is surrounded by what?

Prepuce

Erectile tissue

Contains connective tissue, smooth muscle, and vascular space

Vascular space of eretile tissue fills with what?

Blood

Two erectile bodies

1.) Corpus spongiosum

2.) Corpora cavernosa

Corpus spongiosum

Immediately surrounds urethra

-Distal portion forms glans

Corpora cavernosa

Paired structures that make up most of penile tissue

Accessory glands of male reproductive system

1.) Seminal glands

2.) Prostate

Seminal glands

empty into ejaculatory duct

-Secretions produced

Secretions produced in seminal glands

1.) Fructose

2.) Prostaglandins

3.) Proteins

Prostate glands

Composed of 20-30 glands

-Produce citrate, prostate specific antigen (PSA), and substances that help activate sperm

Smooth muscle and prostate

Smooth muscle walls contract during ejaculation to release contents

Prostate cancer - how many men develop?

1 in 6 men

-Usually develops later in life (age 50+)

Progression of prostate gland

Ranges from slow-growing to highly aggressive

• Men usually die with it, not because of it

Symptoms of prostate cancer

Difficulty urinating, blood in urine and or/semen, erectile dysfunction

-Usually symptomless in early stages

Benign prostatic hyperplasia

Benign growth of prostate

-Constricts prostatic urethra which makes urination difficult and painful

Bulbo urethral glands

Produces alkaline mucus because sperm is sensitive to acidity

Semen

Combination of sperm with accessory gland secretions

Components of seminal secretions and their functions

1.) Prostaglandins

2.) Relaxin

3.) Fructose

4.) Antibiotic components

5.) Clotting factors

6.) Other

Prostaglandins

Decrease viscosity of mucus in female cervix, stimulate reverse peristalsis in uterus

Relaxin (and other enzymes)

Promote and enhance sperm motility

Fructose

Catabolized for sperm ATp synthesis

Antibiotic components

Destroy bacteria that could harm sperm Cl

Clotting factors

Coagulate sperm after ejaculation

“other” part of seminal secretions

Suppression of female immune system (destroy things that do not belong)

Spermatogenesis

Production of male gametes

Important cell types of seminiferous tubules

1.) Sustenocytes

2.) Spermatogenic cells

3.) Myoid cells

4.) Interstitial endocrine cells

Sustenocytes

Surround, support, and nourish developing sperm

What are adjacent sustenocytes joined by? What does this do?

Tight junctions - prevent sperm from escaping

Spermatogenic cells

Sperm forming cells

Myoid cells

Contract to move immature sperm from tubules to epididymis

Interstitial endocrine cells

Secrete testosterone (with small amount of estrogen)

Spermatogenesis - overall process

1.) Spermatogonia divide by mitosis

2.) Primary spermatocytes undergo meiosis I

3.) Secondary spermatocytes undergo meiosis II

4.) Spermatids undergo spermiogenesis L

Look at spermatogenesis chart from class

Spermatogonia dividing by mitosis - Before puberty

All spermatogonia become more spermatogonia

Spermatogonia divide by mitosis - After puberty

Some become Type A daughter cells, others become type B daughter cells

Type B cells will turn into what

Primary spermatocytes

What happens to Type A cells

Forms more spermatogonia

Primary spermatocytes undergoing meiosis I will form what?

Secondary spermatocytes

Secondary spermatocytes undergoing meiosis II will form what?

Spermatids

Spermatids undergoing spermigenesis will produce what?

Functional (but still immature) sperm

Sperm 3 general areas

1.) Head

2.) Midpiece

3.) Tail