genetics and male reproductive system

genetics

The study of heredity; how traits are passed from parents to offspring.

phenotype

physical appearance

chromosome

Coiled mass of DNA and protein (histones). Every cell in an animal's body contains identical chromosomes, except eggs and sperm.

nucleotide

Sugar, phosphate, nitrogenous base.

diploid

2 copies of each chromosome in body cells.

Haploid

1 copy of each chromosome in germ (reproductive) cells.

Genetic Female 23rd Chromosomes

XX

Genetic male 23rd Chromosomes

XY

karyotype

Visual representation of the chromosomes of a species.

What determines the genetic sex of the offspring in mammals?

Eggs carry XX, the sperm is either X or Y. The sperm determines the gender.

What determines the genetic sex of the offspring in birds?

Sperm carries Z, the egg is either Z or W. The egg determines the gender.

gametes

Productive cells provided by the parents.

inheritance

Alleles are passed from one generation to the next.

cell division

mitosis

spermatogenesis

production of sperm

oogensis

production of ova (eggs)

meiosis

Females begin this but it does not begin until puberty.

nonadditive gene effect

Only 1 or a few pairs of genes determine expression of a trait. Ex: Polled or with horns.

additive gene effect

Multiple genes determine expression of a trait. Ex: Milk production

codominance

Occurs when neither allele masks the other and both alleles are expressed in the phenotype.

incomplete dominance

Heterozygote appears as an intermediate between 2 alleles

epistasis

Many gene pairs at different loci (locations) act together to influence gene expression Ex: Coat color

extension gene

pigment production

agoutti gene 

Controls the deposition of melanin (pigmentation)

reproduction

Required for propagation and continuation of a species.

puberty in males

when sperm begins to generate

The brain and gonads (testes and ovaries) secretes hormones;

The reproductive ability becomes regulated from these hormones

where is the hypothalamus

bottom of the brain

What controls all sexual hormones?

hypothalamus in the brain

LH

luteinizing hormone

FSH

follicle-stimulating hormone

GnRH

gonadotropin-releasing hormone, released in the brain

How frequent is a pulse for GnRH in males?

Multiple minutes every 3 hours. Frequently; this is why stallions and intact males are aggressive.

testes 

Produces Sperm and Hormones

How long to produce sperm cells? And how much?

It takes 5-9 weeks to make sperm cells, and healthy male mammals make 1-25 billion/day.

Why are testes outside the body?

To keep them at a lower body temperature to support + create sperm cells.

Where are testes when males are born?

abdomen

gubernaculum

Band of connective tissue that attaches fetal testes to abdomen, then scrotum.

inguinal rings

Passageway from the abdominal cavity into the scrotum.

inguinal hernia

When the abdominal contents protrude, or enter through the inguinal ring.

cryptorchid

Undescended or Retained Testicle, it never dropped and may be stuck.

Where can cryptorchid testes be?

In the abdomen or inguinal rings.

One or two testes are cryptorchid?

unilateral or bilateral

Can retained testicles work?

They can NOT produce viable sperm but DO produce testosterone.

scrotum

The sac of skin that houses and protects the testes.

spermatic cords

Tubular structure extending from the inguinal ring to testes.

what are the spermatic cords

Ductus deferens, cremaster muscle, pampiniform plexus, arteries and veins.

pampiniform plexus 

Testicular veins that branch into a network of veins that surround the testicular artery.

cremaster muscle

Adjusts the position of the restes relative to the body temperature and fear. Brings up towards the body when its cold.

The Path of Sperm

Seminiferous Tubules --> Ducts --> Epididymis -> Ductus Deferens --> Urethra

ductus deferens

Muscular tube that brings sperm to the epididymis.

seminiferous tubules

Where sperm production occurs, tons and tons of tubes.

Where does spermatogenesis occur?

The seminiferous tubules of the testes. Begins at puberty

Testes Include:

Seminiferous Tubules, Interstitial (or Leydig) Cells, and Sertoli Cells

Interstitial (Leydig) Cells

makes testosterone

sertoli cells

makes estrogen

what controls the reproductive system

the brain

epididymis 

Storage site and maturation site; where the sperm learn to swim

urethra

Collects secretions from accessory sex glands and spermatozoa from ductus deferens.

vasectomy

Cutting out a part of the ductus (vas) deferens outflow tract. Still makes testosterone and estrogen, but NOT sperm cells.

Accessory Sex Glands

Glands that contribute secretions and fluid of semen to help sperm along the way.

penis

male breeding organ