lecture 16- development of the female and male system

miller

what reproductive events are occuring during the 1st trimester

migration of primoridal germ cells from yolk sac

sex cords develop in gonad, paramesonephric ducts develop

sex evident from structures

when does the development of male/female ducts and gonads begin

starts in the 1st trimester goes until middle of 2nd trimester

what main thing happens in the second trimester

formation of broad ligament

what is the main thing that happens in 3rd trimester

testicular descent

an organism in the early stages of development

embryo

T/F when they are an embryo placentation has not yet taken place

true

potential offspring within the uterus that is generally recognizable as a member of a given species

fetus

what is fetus marked by

development of placentation

what are the primary embryonic germ layers

what does the embryo start as

mass of cells

primary concern of ectoderm

reproductive tract

• vagina and vestibule

• penis and clitoris

mammary glands

nervous system

• hypothalamus

  • both lobes of the pituitary

secondary concerns of ectoderm

 Oral and nasal cavities

 Skin, hair, nails, sweat

glands

primary concerns of mesoderm

 Gonads (testicles

and ovaries)

 Uterus, cervix,

cranial vagina

 Epididymis, ductus

deferens

 Accessory sex

glands

secondary concerns of mesoderm

 Muscle

 Blood vessels

 Urinary system

 Skeletal system

secondary concerns of endoderm

– Digestive system

– Respiratory system

– Most glands

embryonic period in horses

48 days

gestation length in horses

340 days

embryonic portion % in horse

14%

what are the two main parts of pituitary gland

posterior lobe and anterior lobe

parts of posterior lobe

Neural tissue

• Contains axons and nerve terminals of neurons from hypothalamus

• Neurohypophysis

parts of anterior lobe

• Stomodeal Ectoderm

- Tissue from roof of mouth

- Glandular epithelial cells produce glycoprotein hormones

• Adenohypophysis

formed from an eavagination from the oral cavity

anterior lobe by the rathke’s pouch

porterior lobe formed from diverticulum from floor of brain

infundibulum

what is happening here

stalk of rathke’s pouch regresses and seperates from stomodeal ectoderm

what is happening here

rathke’s pouch becomes closely associated with cells of infundibulum

what is the left arrow

neurohypophysis

what is the right arrow

adenohypophysis

where does the anterior pituitary secrete its hormones

into a blood stream

what do neurosecretory cells produce

ADh and oxytocine

how do ADH and oxitocine get to the blood stream

through secretion from the axon ends into the blood steram

what all is produced by neurosecretory cells

FSH

LH

GH

prolactin

ACTH

TSH

oxytocin

ADH

what hormone deposites directly into the circulation

neurohormones coming from posterior pituitary

what does the anterior pituitary use

hypothalamo hypophyseal portal system

• The process whereby a group of unspecified cells develops into a functional,

recognizable group of cells that have a common function

sex differentiation

• A system that determines the sexual characteristics of an organism which

generally consists of genetic (alleles or genes) or hormonal parameters.

sex determination

• This describes the chromosomal complement of an organism

• The organisms we are concerned with will include the sex chromosomes X and Y

karyotype

describe the alleles genetic constitution of an indiviual meaning it deals with the gene sor alleles that code for specific traits

genotype

• Describes the observed characteristics such as morphology, development,

blood types, behavior, etc

• The expression of these characteristics depends on the genetics (genotype),

but is also affected by the environment

phenotype

produced by the fusion of two different zygotes in a single embryo

chimera

an individual with two different cell lines that orginated from the same individual

mosaic

what is this an example of

chimera

what is this an example of

mosaic

sexual differentiation relies on 3 stages what are the

chromosomal sex

gonadal sex

phenotypic sex

Determined at fertilization in mammals by the type of sex chromosome contributed by

the sperm (XX or XY). The sperm contributes one X or one Y

chromosomal sex

• Determined by the “sex determining region of the Y chromosome” (Sry gene)

• Induces testes formation

gonadal sex

• Determined by substances produced in the male testes to cause regression of female

tract and formation of male tract.

phenotypic sex

when an embryo starts do they instantly have a sex assigned

no

where does primordial cells originate from

yolk sac

what is the migration during the sexually indifferent stage

the primordial germ cells migrate through the hindgut to the undifferntiated gonad within the dorsal body wall

what is the dorsal body wall also known as

the genital or gonadal ridge

pronephros

primitive kidney (1st of 3)

mesonephros

intermediate kidney (2nd of 3)

male- form efferent ducts

female- regress

metanephros

final functional kidney (3rd of 3)

functional kidney

mesonephric ducts (wolffian ducts)

male- epididymis and ductus deferens

female- regress

Paramesonephric ducts (Müllerian ducts)

Located beside the mesonephric ducts “para” (along/beside)

Male – regress

Female – uterus and oviducts and cranial vagina

primitive sex cords

male - seminiferous tubules

female- regress, primitive follicular cells

primitive germ cells

male- spermatogonia

female- oocytes

what causes degeneration of the paramesonephric duct

anti mullerian hormone (AMH)

what causes development of the penis, scrotum, and accessory sex glands

dihydrotestosterone

explain male chromosomal pair

explain female chromosomal pair

if a chromosome has SRY what does that mean

its a boy

what produces AMH

sertoli cells

presence of testosterone causes

regression of the female duct system

what will become seminiferous tubules

rete tubules and the mesonephric tubules will interconnect and become seminiferous tubules

what does the mesonephric transform and become

epididymis and ductus deferens

prior to descent where do testes lie

in the retroperitoneal position. The gubernaculum connects the fetal testis to the peritoneum.

after the gubernaculum goes through the inguinal ring there is what

rapid growth of the distal gubernaculum

once the testes are in the inguinal region what happens

they are pulled through the inguinal canal due to the gubernaculum shrinking. Abdominal pressure from visceral growth also provides and extra push for the testes.

what is the efault sex

female

what pulls the testes into the scrotum

continuing to shrink the guernaculum keeps pulling the testes into the scrotum

what are the testes surrounded by in the scrotum

a double layer of peritoneum

to be a female what main things but not be present

testosterone, AMH and DHT

what form the cervix

paramesonephric/ mullarian ducts fusing together

what does the caudal vagina originate from

urogenital sinus that invaginates from the exterior skin

what type of epithelium is caudal vagina

stratified squamous

what does the paramesonephric ducts eventually become

uterus

cervix

or

cranial vagina

what is the genital fold

the two layers that are encapsulating the reproductive tract

what happens to males during fetal maturation

the testicles descend into the scrotum

what happens to females during fetal maturation

the broad ligament develops

the ovaries migrate caudally due to fetal growth