Bio 233 - Chapter 27 Exam 4

William C. Young

Researcher responsible for identifying the ORGANIZATIONAL EFFECTS of gonadal steroids... which are critical for sex differentiation

What is the Organizational-Activational Hypothesis?

It states that steroid hormones permanently organize the nervous system during early development, which is reflected in adult male or female typical behavior. In adulthood, the same steroid hormones activate, modulate, and inhibit these behaviors

What are the three "organizational" component aspects that Young and his colleagues studied?

- Organizational effects are permanent

- Organizational effects occur prior to birth in the prenatal environment or very shortly after birth in what is called the perinatal environment

- Organizational effects take place during a critical period of time during development

Activational effects are the effects that occur at -

the onset of puberty in mammals (including humans) and are maintained through the reproductive lifespan of the individual

Activational effects are what cause -

final maturation of the gametogenic activity and guide sexual maturation

The activational effects of steroid hormones also stimulate -

the development of the emotions of sexual interest and sexual desire many people experience in adulthood

Overall, it is the mix of the organizational and activational effects of steroid hormones that -

determine sexual growth and development in both males and females

Organizational effects of steroid hormones occur in _______ while the onset activational effects of steroid hormones occur at ______

early life; puberty

The steroid hormones released at the two distinct times are important for shaping -

the biological aspects of our sex determination, sex differentiation, sex orientation, and gender identity

Trace the movement of material starting with the production of a sperm cell in the testis and moving outward from that point

Seminiferous Tubules in the testes (site of sperm production we will see in a few moments) -> Epididymis -> Ductus (or Vas) Deferens -> Seminal Vesicle -> Prostate Gland -> merge with the urethra in a section called the Prostatic Urethra -> the Bulbourethral Gland connects to the prostatic urethra as it enters the Penis and becomes simply the Urethra.

Seminiferous Tubules

The specific location gamete production (meiosis) leading to the development of male gametes... spermatozoa

Testes

The primary reproductive organ of the male that consists of a pair of sperm-producing organs. The testes are known as the male gonads

Epididymis

A highly convoluted duct behind the testis, along which sperm passes to the ductus (or vas) deferens

Ductus (or Vas) Deferens

A tiny muscular tube in the male reproductive system that carries sperm from the epididymis to the ejaculatory duct

Seminal Vesicles

Glands which open into the Vas Deferens near to it junction with the Urethra and secretes seminal fluid... the largest part by volume of a male's ejaculate

Prostate Gland

A walnut-sized gland located between the bladder and the penis. The secretions of the prostate produces lubrication and nutrition for the sperm

Prostatic Urethra

The part of the urethra that passes through the prostate

Bulbourethral Gland (also called Cowper's Gland)

Function to lubricate the spongy urethra for the passage of the ejaculate

Urethra

The tube that is in males used to transport both urine and ejaculate

Penis

The male genital organ of higher vertebrates, carrying the duct for the transfer of sperm during copulation

Scrotum

The part of the external male genitalia located behind and underneath the penis

The scrotum is biologically homologous to the _____ _____ in females

labia majora

What is the function of the scrotum?

It regulates the temperature of the testes and maintains it at 35 degrees Celsius (95 degrees Fahrenheit

Temperature control is accomplished by the scrotum by using the -

cremaster muscle of the scrotum to move the testicles either closer to or further away from the abdomen depending on the environmental temp

Seminiferous Tubules are located within the -

testes

Seminiferous Tubules are the specific location of -

meiosis, and the subsequent creation of male gametes, namely spermatozoa

Spermatogenesis

The process for producing spermatozoa

The Seminiferous tubules are connected to the -

epididymis which consists of tubes that connect a testicle to a vas deferens in the male reproductive system

The epididymis is a single, narrow, tightly coiled tube and in adult humans, if uncoiled, would be _______ in length

20 ft

The epididymis is present in -

all male reptiles, birds, and mammals

What is the primary sexual organ that male animals use to inseminate females during copulation?

The penis

Sperm are what type of cell?

Haploid

What is a haploid cell?

Having 1 set of chromosomes (so 23 total for humans) (n) "HAlf of the total"

What is a diploid cell?

Have 2 sets of chromosomes (46 total for humans; 23 PAIRS) (2n)

Meiosis produces what type of cell?

Haploid cells (Sperm) (n)

Mitosis produces what type of cell?

Diploid cells (2n)

Many animals, both vertebrate and invertebrate, have penises, but males do not bear a penis in every animal species, and in this species in which the male does bear a so-called penis -

the penises in the various species are not necessarily homologous

Ther term penis applies to -

many intromittent (a reproductive behavior) organs, but not to all

Corpus Cavernosa

One of a pair of sponge-like regions of erectile tissue, which contain most of the blood in the penis during an erection

What are the two erectile tissues called?

- Corpus cavernosa

- Corpus spongiosum

Blood can leave the erectile tissue only through -

a drainage system of veins around the outside wall of the corpus cavernosum

During an erection, the expanding spongy tissue -

presses against a surrounding dense tissue (tunica albuginea) constricting the drainage veins, preventing blood from leaving, making the penis become rigid

Corpus Spongiosa (also called Corpus Cavernosum urethrae in older texts)

The mass of spongy tissue surrounding the male urethra within the penis

What is the function of the corpus spongiosum in erection?

To prevent the urethra from pinching closed, thereby maintaining the urethra as a viable channel for ejaculation

Gonads produce -

gametes

What are gametes?

Eggs or Sperm

Meiosis produces how many haploid daughter cells?

4

Steps of Meiosis (sexual reproduction)

- Prophase I

- Metaphase I

- Anaphase I

- Telophase I

- Cytokinesis I

- Prophase II

- Metaphase II

- Anaphase II

- Telophase II

- Cytokinesis II

Steps of Mitosis (asexual reproduction)

- Prophase

- Metaphase

- Anaphase

- Telophase

- Cytokinesis

What happens in Meiosis Prophase I

Chromosomes pair up in homologous pairs, and crossing-over occurs

What happens in Meiosis Metaphase I

Homologous pairs align at the equatorial plane

What happens in Meiosis Anaphase I

Homologous chromosomes separate to opposite poles

What happens in Meiosis Telophase I

Nuclear membranes reform, followed by cytokinesis

What happens in Meiosis Prophase II

Chromosomes condense; nuclear envelope dissolves

What happens in Meiosis Metaphase II

Chromosomes align at the equatorial plane

What happens in Meiosis Anaphase II

Sister chromatids separate

What happens in Meiosis Telophase II

Nuclear membranes reform, followed by cytokinesis, resulting in four non-identical daughter cells

What happens in both Meiosis and Mitosis Interphase?

DNA replication occurs, preparing the cell for division

What is gametogenesis?

A biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes

When we are specifically talking about male gametogenesis, we refer to this as -

spermatogenesis

The mitotic division of spermatogonia stem cells produces which two types of cells?

- Type A cells that replenish the stem cells

- Type B cells that differentiate into primary spermatocytes

The production of sperm occurs within the -

basal component and adluminal component of the seminiferous tubules

The sperm head is actually primarily -

genetic material with very limited amounts of cytoplasm. It also makes up about 10% of the total sperm length

The midpiece region of the sperm is the -

central part of the sperm cell between the head and the tail that contains tightly packed mitochondria that provide the energy required for swimming, and makes up about 10% of the total sperm length

What is the end of the sperm called?

The flagellum, also called the sperm "tail" and is a slender lash-like appendage that protrudes from the cell body

Androgen Insensitivity Syndrome (AIS)

An intersex condition where there is a partial of complete inability of the cell to respond to androgens (testosterone and dihydrotestosterone)

How often does Androgen Insensitivity Syndrome (AIS) occur?

Estimated to occur in about 1 of every 50,000 births

Individuals with AIS develop the external genitalia of the female, but do not develop -

functional ovaries nor a uterus and are therefore infertile

What are the effects of Androgen Insensitivity Syndrome? (AIS)

It can impair or prevent the musculation of male genitalia in the developing fetus, as well as impairing or preventing the development of male secondary sexual characteristic at puberty

What are the External Genitalia of Males?

- Penis

- Scrotum

What are the Internal Genitalia of Males?

- Testes

- Epididymides

- Ductus deferentes

- Seminal vesicles

- Prostate

- Bulbourethral glands

What are the External Genitalia of Females?

- Mons pubis

- Labia majora

- Labia minora

- Clitoris

- Vaginal orifice

- Vestibular bulbs

- Vestibular glands

- Paraurethral glands

What are the Internal Genitalia of Females?

- Ovaries

- Uterine tubes

- Uterus

- Vagina

What is the PRIMARY reproductive organ in males?

The testis

What hormones are produced by the testes?

Androgens (testosterone, androstenedione)

Libido

The desire to engage in reproductive and sexual behavior

Androgens from the testes will drive the development of the male typical secondary sexual characteristics during the ACTIVATIONAL stage. These characteristics include:

- Libido

- Growth and development of male pattern body hair

- Male-typical muscle mass development profile

- Growth and functional development of the male external genitalia

Sex determination

The process by which the sex of an individual is determines

Sex determination system

A biological system that determines the development of sexual characteristic in an organism

Most organisms that create offspring using sexual reproduction have how many sexes?

2

In many species, sex determination is -

genetic

Humans use what is called the -

XY Sex Determination system

In some species, sex of a fetus is determined by -

environmental variables (such as temperature)

In an embryo biology context, the word "indifferent" is to convey the idea that -

the embryo is neither developing in the male-typical direction nor is it developing in the female-typical direction

What happens if the gonad does not differentiate, or does not grow?

In the case of mammals (or any organism with X-Y Sex Differentiation), the body morphology develops towards a more female-typical development

Efferent ductules form connections with the testes that will become a series of parallel, thin, tubules that connect the testis to a single tube called the -

epididymis

When spermatozoa are produced in a functional testis, they will exit the testis via the -

efferent ductules

Around weeks 8-9, the Mullerian Ducts will continue to grow and the funnel like ends will eventually grow to surround one end of each ovary with -

"finger-like" projections called the Fimbrae

When a mature, functional ovary releases an ova (egg), it will travel down the fimbrae into what is called -

the Mullerian tubulature

WIth more development, the Mullerian tubulature becomes what is more commonly refered to as -

the Fallopian (or Uterine) Tube

The developmental path towards more female-typical development occurs _________ than the developmental path towards male-typical development

LATER

The DEFAULT PATTERN for an X-Y Sex Determining species is -

female

Internal gonadal differentiation occurs around week -

7

External gonadal differentiation occurs around week -

8-9

Urogenital triangle

The anterior half of the perineum. It is bounded by the pubic symphysis, ischiopubic rami, and a theoretical line between the two ischial tuberosities

Anal triangle

The posterior half of the perineum, by definition

The perineum

In humans, it is the space between the anus and scrotum in the male and between the anus and the vulva in the female

Anogental distance

A measure of the distance between the midpoint of the anus and the underside of the scrotum or the vagina

The is a _______ range of perineum size in both sexes with some overlap in size between sexes

GREAT

What is the role of the scrotal sac in male reproductive health?

Protect the testes and optimize conditions for sperm production