Ch. 28: Reproductive System

What are the 4 major functions of the reproductive system?

1. gametogenesis

2. fertilization

3. development and nourishment of a new individual

4. production of reproductive hormones

Meiosis ⭐️

specialized cell division for producing gametes

Gametes ⭐

reproductive cells with half of the DNA content of non-reproductive cells

Homologous chromosomes

pairs of chromosomes with the same size/shape/gene sequence, but may have different versions of genes (blue vs green eyes)

Chromatid

one half of a chromosome, sometimes referred to as “single-stranded chromosomes”

How many homologous pairs of chromosomes do human somatic hells have?

23 homologous pairs of chromosomes

(22 autosomal pairs and 1 sex pair)

Homologous pairs

one chromosome from each parent, both containing corresponding genetic information

Upon fertilization, how many haploid gametes combine to form a diploid gamete?

2 haploid gametes combine to form a diploid gamete

What are the 2 divisions of meiosis?

Meiosis I and Meiosis II

True/False: Meiosis I produces 2 haploid daughter cells with 23 unpaired chromosomes

True

Reductive division

reduction of cell chromosomes during meiosis

Crossing over ⭐

exchange of genetic material between maternal and paternal chromosomes

True/False: Meiosis II continues with 2 haploid daughter cells with 32 unpaired, double-stranded chromosomes from Meiosis I

True

Meiosis II produces how many daughter cells and how many chromatids?

produces 4 daughter cells each with 23 chromatids

Independent assortment

random separation of homologous chromosomes during meiosis I

What are the 4 major components of the male reproductive system?

1. testes

2. ducts

3. accessory glands

4. supporting structures

Ducts in the male reproductive system

• epididymides (epididymis)

• ducts deferentia

• urethra

Accessory glands in the male reproductive system:

• seminal vesicles

• prostate glands

• bulbourethral glands

Supporting structure of the male reproductive system:

• scrotum

• penis

Scrotum

• saclike structure that contain the testes

• formed by skin, connective tissue, and a layer of muscles

Cremaster muscle

extension of skeletal muscles that attach to the testes and control their distance from the body

Perineum

area between the thighs, pubic symphysis, coccyx, and ischial tuberostites

What are the 2 areas of the perineum?

1. urogenital triangle

2. anal triangle

Urogenital triangle

anterior portion containing the base of the penis and scrotum

Anal triangle

posterior portion containing the anal opening

Testes

• small, oval-shaped organs within the scrotum

• function as exocrine and endocrine glands

• male gonads

Seminiferous tubules

site of sperm cell formation; contained within the lobules

Interstitial (Leydig) cells

clusters of endocrine cells near seminiferous tubules which secrete testosterone

Spermatogenesis

development of sperm cells

What 2 cells within seminiferous tubules are important for sperm formation?

1. germ cells

2. sustentacular (Sertoli) cells

Germ cells

cells that undergo meiosis to form 4 haploid daughter cells

Sustentacular (Sertoli) cells

nourish germ cells and produce some hormones (not testosterone)

Sex hormone binding globulin

protein secreted by sustentacular cells to increate sex hormones half-life

Spermatogonia (spermatogonium)

germ cells undergoing mitotic division

Spermatids

• 4 haploid daughter cells produced from single primary spermaocyte

• produced by second meiotic division; contain 23 chromatids (single-stranded chromosomes)

Spermiogenesis

last phase of spermatogenesis that produces a sperm cell

Spermatozoon (spermatozoa)

sperm cells

During spermiogenesis, each spermatic develops 3 structures:

1. head- contain acrosome

2. midpiece

3. flagellum (tail)- allows sperm cell self-propelled motility

Acrosome

specialized vesicle with enzymes that allow the sperm cells to penetrate the oocyte (egg)

Epididymis

• comma-shaped structures on the posterior aspect of each testis

• contain cilia to help move sperm along ducts

Final sperm cell maturation occurs in the ________

epididymis

Ductus deferens

connects epididymus to ejaculatory duct

Ampulla

enlargement of the deferens where it approaches the ejaculatory duct near the prostate

What are the 3 sections of the male urethra?

1. prostatic urethra

2. membranous urethra

3. spongy urethra

Prostatic urethra

connected to the bladder; passes through the prostate gland

Membranous urethra

shortest portion that connects prostatic and spongy urethra

Spongy urethra

longest portion; opens into eternal urethral orifice

Penis

male organ of copulation

Copulation

transfer of sperm cells from male to female for fertilization

What 3 columns of erectile tissue are found in the penis?

• corpus cavernosa (2)

• corpus spongiosum (1)

Corpus cavernosa

2 large columns forming the majority of erectile tissue

Corpus spongiosum

1 column surrounding the urethra and extends to form the head of the penis

Glans penis

distal end of the penis formed by corpus spongiosum

What are the 3 major glands required for normal reproductive function?

• seminal vesicles

• prostate gland

• bulbourethral glands

Seminal glands

sac-like glands near the ampullae and prostate

Prostate gland

walnut-shaped/sized doral to the pubic symphysis

Bulbourethral glands

pair of pea-sized glands near the membranous urethra

Semen

collective secretions from seminiferous tubules in testes and accessory glands

Seminal vesicles

secrete thick fluid with 3 major functions:

• nourish sperm cells

• coagulate semen

• movement of sperm cells

Movement of sperm cells

enzymes to help sperm reach female reproductive tract via urine contractions

Hormones are responsible for:

• development of reproductive structures

• maintenance of reproductive functions (sperm cell formation)

• development of secondary sexual characteristics

Neural mechanisms are responsible for:

• sexual behavior

• control of the sex act

What are the 3 important hormonal mechanisms/systems that influence the male reproductive system?

• hypothalamus

• pituitary gland

• testes (male gonads)

Hypothalamus

releases gonadotrophin-releasing hormone (GnRH)

Pituitary gland

releases 2 gonadotrophin hormones in response to GnRH

Testes

releases testosterone in response to LH

Luteinizing hormone (LH)

stimulated testosterone production/release

Follicle-stimulating hormone (FSH)

stimulated sperm cell development

What are some wide range effects of testosterone?

• enlargement of genitals and development of the duct system

• development of secondary sexual characteristics

• growth of thicker, coarser, pigmented hair in pubic area, axillary region, face

• increases sebaceous gland production, especially in the face

• hypertrophy of the larynx

The male sex act is involved in a sequence of 4 major reflexes:

• erection of the penis

• secretion of mucus into the urethra

• emission

• ejaculation

Emission

discharge of secretions from the ducts deferential into the urethra

Ejaculation

forceful expulsion of semen from the urethra

____________ action potentials induce bulbourethral secretions

Parasympathetic

Sympathetic centers control ______ and ________

emission and ejaculation

Sympathetic centers induce what?

• seminal vesicle and prostate gland secretion

• peristaltic contractions of reproductive ducts

Somatic motor action potentials control what?

ejaculation

Sex act = ________ + _________ +_________

parasympathetic + sympathetic + somatic

The anatomy of the female reproductive system includes:

• ovaries

• uterine tubes

• uterus

• vagina

• external genital organs

• mammary glands

Ovaries

female gonads

The overies are supported by 3 structures such as:

• mesovarium

• suspensory ligament

• ovarian ligament

Mesovarium

peritoneal fold anchoring the ovaries to the broad ligament

Suspensory ligament

anchors mesovarium to the abdominal wall

• carries ovarian arteries, veins, and nerves

Ovarian follicles

structures containing developing primary oocytes

• distributed through the cortex

Oogenesis

process of female gamete production

• begins before birth

Ovaries contain ________ oocyte germ cells (oogonia) 4 months following fertilization

~5 million

Primary oocytes

diploid female sex cell that undergoes meiosis I

Female meiosis results in 2 uneven cells:

• secondary oocyte

• first polar body

Secondary oocyte

larger cell created by meiosis I

• also called “ovum”

First polar body

smaller cell with less cytoplasm

Ovulation

release of a secondary oocyte from an ovary

Meiosis II is only completed if _________________

the secondary oocyte is fertilized

Fertilization

process of sperm binding to and penetrating a secondary oocyte

Zygote

fertilized ovum with 23 pairs of homologous chromosomes