Male Reproduction

• survival of species

• production of sex cells (gametes)

• transport the gametes toward each other

• allow gametes to meet (fertilization)

• promote the generation, maintenance, and rearing of progeny

What are the functions of male reproduction?

23 (1/2 the DNA the parent cell has)

If there are 46 chromosomes, how many chromosomes in each gamete?

meiosis

like mitosis (creating new cells)

• the progeny cells will have ½ the number of chromosomes

gonads (testes=male, ovum=female)

Where are the gametes made and where does meiosis take place?

fertilization

meeting of the sperm and ovum that reestablishes the diploid number (23 chromosomes in female + 23 chromosomes in male = 46 = diploid number)

only one time

How many times is the DNA divided during Meiosis?

• start with x-shaped chromosomes (2 DNA/chromosome)

• assorts chromosomes by homologous pairs (1 mom & 1 dad)

• pairs are separated randomly, which reduces the number of chromosomes in half

  Diploid (2n/46) to Haploid (n/23)

Explain the steps of Meiosis I (diploid # —> haploid #)

• sister chromatids are separated

• Progeny cells are created and have one piece of DNA per chromosome.

Explain the steps of Meiosis II (looks like mitosis/splitting of the DNA)

2 cells, each have ½ the number of chromosomes, still have 2 DNA per chromosome

What do you end with at the end of Meiosis I?

Interphase, Prophase I, Crossover, Metaphase I, Anaphase I, Telophase I & Cytokinesis

What are the steps of Meiosis I?

x-shaped chromosomes duplicate

What happens in Interphase I?

Homologous (mom and dad) chromosomes pair and exchange segments

• Exchanging segments aids in enzyme control (stops the making of mutations/error in the code for genes; can be good, bad, or neutral; sometimes pieces go the wrong way)

• ex. Down Syndrome extra 21st chromosome

What happens in Prophase I?

Crossover

occurs in Meiosis I; when genes jump and makes new combinations of genes

• causes genetic diversity in our species

Tretrads line up in the middle as homologous pairs

What happens in Metaphase I?

pairs of homologous chromosomes split up

• # of chromosomes is reduced

What happens in Anaphase I?

• Two haploid cells form (have ½ the # of chromosomes that the diploid cell has)

• nuclear envelope comes back, genes uncoil, establish new membrane, mitotic spindle destroyed

• end up with 2 cells with half the number of chromosomes as the cell started with but still have 2 pieces of DNA per chromosome

What happens in Telophase I and Cytokinesis?

Meiosis I

# of chromosomes is split in half

Meiosis II

splitting of DNA

same as mitosis

What happens in Prophase II and Metaphase II?

sister chromatids separate and move towards the poles

What happens in Anaphase II?

Haploid daughter cells form

• ends with 4 cells

• each cell has ½ the DNA as the parent cell (1 DNA per chromosome)

• genetically different than it was before

What happens in Telophase II and Cytokinesis?

Each cell turns into sperm or an ovum

At the end of Meiosis II, what does each cell turn into?

testis and spermatozoa

What is the gonad and gamete in the male?

duct system

part of the male reproductive system that stores and transports sperm from the gonad to the external environment

no

Are there stores of energy inside a sperm?

• allow sperm maturation (sperm have flagella, head with supercoiled DNA, cap, motor)

• allow survival of sperm in the external environment

• deposit sperm into the female vagina

• sensory functions (reinforce the need to survive as a species —> feels good so people will want to reproduce)

What do the supporting structures in the male reproductive system do?

temperature control; keeps testis away from the body (4 degrees F)

What is the function of the scrotum?

helps with sperm maturation

What does the epididymis do?

add fluid to volume

What do the Bulbourethral gland, prostate gland, and seminal vesicles do?

seminal fluid

helps support the sperm and neutralize the female genital tract

• allows for penetration of the vagina

• allows for urination

• erects during sex and deposits sperm

What does the penis do?

head, middle piece, tail

What are the three parts of the penis?

motor molecules, base of flagella, mitochondrion

What are parts of the middle piece of sperm?

acts as a propellor

What does the tail of the sperm do?

spins, drives the sperm forward, provides energy (ATP)

What does the mitochondrion (in the middle piece of the sperm) do?

centriole, nucleus (compacted DNA), acrosome

What are the parts of the head of the sperm?

• like a cap

• storage area of enzymes and proteins

• These enzymes and proteins allow the sperm to find the egg, bind to it, and make the sperm able to get through the membrane of the egg.

What is the role of the acrosome in the head of the penis?

in the testis

Where does spermatogenesis occur?

Spermatagonia, Primary Spermatocytes, Secondary Spermatocytes, Spermatids, Spermatazoa

What are the steps of spermatogenesis?

mitosis (starts at adolescence), releases one cell, no

How does Spermatagonia turn into Primary Spermatocytes?

Do the # of chromosomes/cell or # of chromatids/chromosome change?

through Meiosis I (1st mitotic division)

46 chromosomes/cell in primary spermatocytes, 23 chromosomes/cell in secondary spermatocytes

still 2 chromatids/chromosome

How do Primary Spermatoctyes turn into Secondary Spermatocytes?

How do the # of chromosomes/cell or # of chromatids/cell change?

23, 2

How many chromosomes per cell and chromatids (DNA) per chromosome do Secondary Spermatocytes have?

Meiosis II (2nd mitotic division)

same # of chromosomes/cell as secondary spermatocytes (23), but now there is only 1 chromatid per chromosome

How do Secondary Spermatocytes turn into Spermatids?

How do the # of chromosomes/cell or # of chromatids/chromosome change?

Differentiation (change shape of the cell, gets rid of things they don’t need such as protein manufacturing facilities, rER, ribosomes, most of the cytoplasm, grow flagella)

both numbers stay the same (23 and 1)

How do Spermatids turn into Spermatazoa?

How do the # of chromosomes/cell or # of chromatids/cell change?

4 cells (immature sperm)

In spermatogenesis, how many spermatid cells do you end up with? (step right before spermatazoa)

differentiation

happens when spermatids turn into spermatozoa

• change shape of the cell, gets rid of things they don’t need such as protein manufacturing facilities, rER, ribosomes, most of the cytoplasm, grow flagella

Spermiogenesis

process of a spermatid turning to a mature sperm

mitochondria (moves together, comes into full spiral form and gets ready to provide energy (ATP) to the sperm

What is a big part involving Spermiogenesis?

in between seminiferous tubules

Where are Leydig cells found?

• secrete pheromones (hormones)

• help to modify the production of sperm

• gives sperm nutrients

• takes away waste (maturation)

What do Sertoli cells do? (supporting cells that are involved with the seminiferous tubules)

secrete testosterone needed for blood and production of sperm

What do Leydig cells do? (the cells located between the seminiferous tubules)

human testis

septum dividing testis into lobules

exit points, leads to the epididymis on the outside

What are the functions of the efferent ducts?

seminiferous tubule

inside lobules, very long tube

• drains all the lobules

• grid of tubes that stage the sperm

• helps generate active flagella in the sperm

What are the functions of the Rete testis?

ductus (vas) deferens

structure located behind the bladder that carries sperm from the epididymis to the ejaculatory duct and passes through the inguinal canal duct into the peritoneal cavity

Epididymis

the storage area for maturing sperm, starts off as several tubes, goes to one

• when sperm is here, the acrosome is further activated (likely for sperm to find ovum)

there is not blood supply

options are to reestablish blood supply or remove the testis

Why does the testis spin in the scrotum in some males?

add seminal fluid to form semen

What do accessory sex glands do?

90-95

Seminal fluid accounts for __-__% of semen volume.

Seminal fluid

includes water, alkaline buffers, mucous, fructose, prostaglandins and enzymes

neutralize male urethra and female vaginal tract

What do alkaline buffers (in seminal fluid) do?

protects linings

What does mucous (in seminal fluid) do?

nourishes sperm

What does fructose (in seminal fluid) do?

• most powerful hormonal stimulation for smooth muscle

• causes smooth muscle to contract

• helps ejaculation happen, helps contractions in the female vaginal tract

• moves sperm

What is the role of prostaglandins in seminal fluid?

Seminal Vesicle - 60%

Prostate gland - 30%

Bulbourethral (Cowper’s) gland - less than 5%

What are the three glands in the male reproductive system and what percentage of semen volume do they each make up?

help neutralize the urethra

(all have alkaline properties)

• Without these, the high acidity would kill the sperm.

All of the glands are connected to the urethra. What do they do?

alkaline (neutralize) and mucous (lubricate)

What does the Bulbourethral Gland have?

Prostate

structure located underneath the bladder

• series of tubes that bring fluid secretions to the urethra and ejaculatory ducts

• enlarges during sex and blocks off the urethra so no urine comes out

prostatic (base), membranous (penetrates the body wall and shortest part), penile (goes through the penis)

What are the parts of the male urethra?

provides physical support to the testes and regulates testicular temperature

What is the function of the scrotum?

Cremaster muscle

What is the muscle that can change the testis temperature depending on what position it is in?

• in spermatic cord

It elevates the testis close to the body (to warm) and farther away (to cool).

How does the Cremaster muscle change the temperature of the testis?

Pampiniform Plexus

acts as a heat counter current exchanger with the testicular artery

• in spermatic cord

blood vessels, nerves, vas deferens

What is in the spermatic cord?

corpus spongiosum

type of erectile tissue that wraps around the penis

• enlarges at the tip into glans penis

• has a bulb at root of penis

Corpora Cavernosa

type of erectile tissue that offers structural support for the penis

• has a Y at the base (Crura at root of penis)

• causes the erection

circumcision

removal of the foreskin

smegma

unwashed foreskin (dead skin cell buildup)

• possibility of infection

hypothalamus

secretes GnRH into anterior pituitary

triggers gonad to release hormone

affects sex hormone levels

What does GnRH do?

FSH (follicle stimulating hormone) and LH (luteinizing hormonefollicle-stimulating

What are the two sex hormones that the gonad releases?

ABP (antigen binding protein)

Sertoli cells secrete what protein that makes sure testosterone remains high in the seminiferous tubule?

Sertoli cells can make a counter hormone (inhibin), which inhibits the operation and stops the production of FSH

What can the Sertoli cells do regarding hormones?

• this turns off FSH production

spermatogenesis

Since the ABP (antigen binding protein) makes sure testosterone is high in the seminiferous tubule, what process is stimulated?

Leydig cells

Sex hormone LH: what type of cells are involved with this sex hormone? (they make testosterone)

seminiferous tubule, sexual, inhibit, FSH, LH

pathway of testosterone with Leydig cells: Some testosterone stays in the _______________ ____________; the rest goes to the bloodstream to create secondary __________ characteristics of the male.

Testosterone from the blood also feeds back to the Anterior Pituitary and Hypothalamus to __________ both production of ___ and ___productions.

arousal, plateau, orgasm

What are the 3 steps in the sexual response?

• touching of the genital skin

• mechanical stimulation of pressure receptors in the penis

• erotic sights, sounds, and smells

• thoughts and memories

What is arousal (sexual excitement) triggered by?

myotonia (muscle tension) throughout body, blood pressure, breathing, heart rate

What increases during arousal?

• increased accumulation of blood in erectile tissues

• Bulbourethral gland secretes small amount of mucoid fluid to neutralize male urethra and lubricate glans

• The testes are drawn upward (towrads body) by increased contractions of the vas deferens and cremaster muscles

What happens in the plateau stage (erection) of the male sexual response?

ejaculation - rhythmic contractions propel semen out of the penis

What happens in orgasm?

positive

What type of feedback is an erection an example of?

the brain and the sacral spinal cord

What is the erection reflex controlled by?

Parasympathetic, reduce

Erection: _______________ (through the local release of NO) vasodilation of arterioles leading to the erectile tissue of the penis.

As the corpora cavernosa enlarge, they ______ blood flow through the penile veins which increases engorgement.

critical point

Male orgasm begins when stimulation reaches a ______ _____.

This is accompanied by feelings of inevitability.

emission and ejaculation

What are the 2 parts of the spinal reflex?

emission

movement of semen into the urethra

ejaculation

expulsion of semen from the urethra

urethra, sympathetic

During emission, the vas deferens, ejaculatory duct, prostate, and seminal vesicle contract and push their fluids into the ____________ through ___________ stimulation.