Reproductive System. Mammary Glands Present in both sexes, but only function in females Modified...

Reproductive System

Mammary Glands

Present in both sexes, but only function in females

Modified sweat glands

Function is to produce milk

Stimulated by sex hormones (mostly estrogens) to increase in size

Skin (cut)

Pectoralis major muscleConnective tissuesuspensory ligamentAdipose tissueLobeAreolaNipple

Opening oflactiferous ductLactiferous sinusLactiferous ductLobule containingalveoli Hypodermis

(superficial fascia)Intercostal muscles

First rib

(a) (b)

Reproductive System Function

Endocrine system plays a large role

2 hormones:

Follicle Stimulating hormone – helps produce sperm and oocyte (egg)

Luteinizing hormone – helps produce testosterone and induce ovulation

Male Reproductive FunctionsChief role – to produce sperm and testosterone

Spermatogenesis

Sperm production

Begins during puberty and continues throughout life

Only one sperm fertilizes an egg but a man make millions everyday

Involves meiosis – special nuclear division that halves the chromosomes

This process produces 4 functional sperm

Sperm pack light – the sperm head contains compacted DNA (nucleus)

Anterior to the nucleus is the helmet like acrosome

When sperm comes into contact with a oocyte the membrane of the acrosome breaks down the follicle (outside) cells of the egg

(a)

(b)

Plasma membrane

Tail

Axial filamentof tail

Mitochondria

Proximal centriole

NucleusAcrosomeDistal

centriole

Midpiece

NeckHead

Testosterone Production

Produced by the interstitial tissue of the testes but also released by the pituitary gland

Starts in puberty (in response to LH) and produced continuously (more or less) throughout life

Rising levels stimulate adolescent growth spurt, prompts reproductive organs to develop, underlies sex drive, and causes secondary sex characteristics

Secondary Sex characteristics

Deepening of voice

Increased hair growth

Enlargement of skeletal muscles

Increased bone growth and density

Female Reproductive Functions and Cycles

Ovarian Cycle

The total supply of eggs are present at birth

Ability to release eggs begins at puberty

Reproductive ability ends at menopause

Ovarian cycle

Cycle of how a egg undergoes change from an oocyte in the ovary, to an oocyte that is expelled for ovulation

This is triggered by LH and FSH

FSH starts the change

LH expels it from the ovary

(b) Ovarian cycle: Structural changes inthe ovarian follicles during the ovarian cycleare correlated with (d) changes in theendometrium of the uterus during theuterine cycle.

Primaryfollicle

Secondaryfollicle

Vesicularfollicle

Corpusluteum

Ovulation Degeneratingcorpus luteum

Lutealphase

Ovulation(Day 14)

Follicularphase

After expulsion from the ovary the oocyte travels down the fallopian tube

If fertilized, produces an ovum which combines with the 23 chromosomes of the sperm to form a fertilized egg (46 chromosomes)

Meiosis here only produces one functional egg and 3 polar bodies (non functional)

If not penetrated by a sperm it simply breaks apart

(d) The three phases of the uterine cycle:•Menstrual: Shedding of the functionallayer of the endometrium.•Proliferative: Rebuilding of thefunctional layer of the endometrium.•Secretory: Begins immediately afterovulation. Enrichment of the bloodsupply and glandular secretion ofnutrients prepare the endometrium toreceive an embryo.

The menstrual and proliferative phases occurbefore ovulation, and together correspond tothe follicular phase of the ovarian cycle. Thesecretory phase corresponds in time to theluteal phase of the ovarian cycle.

Menstrualflow

Basal la

yer Fu

ncti

on

al la

yer Endometrial

glands

Menstrualphase

Proliferativephase

Secretoryphase

1 105 2515 20

Blood vessels

28 Days

Uterine (Menstrual) Cycle

The window for implantation is only for a very short period each month

Occurs approx. 7 days after implantation

Menstrual cycle – cyclic changes that the endometrium goes through month after month, responding to changes in the levels of ovarian hormones in the blood

Progesterone and Estrogen (produced in ovaries) is regulated by FSH and LH

Estrogen produced in response to FSH

Progesterone in response to LH

Generally both female cycles occur in 28 days

Ovulation typically occurs midway in the cycles (day 14)

Days 1-5

Endometrial layer is sloughing off

Accompanied by bleeding for 3-5 days

Day 6-14

Proliferative phase

Stimulated by a rise in estrogen levels produced by growing follicles of the ovaries

Endometrium starts to regenerate and blood supply increases

Ovulation occurs in the end of this stage in response to the sudden surge of LH in the blood

Day 15-28

Rising levels of progesterone act on the estrogen primed endometrium and increase its blood supply even more

It is the uterus preparing for fertilization and implantation

If fertilization does not occur ovarian hormones decrease which causes the blood supply in the endometrium to go into spasms and kink. Endometrial cells begin to die and sets the stage for menses to begin again on day 28

Secondary sex characteristics

Enlargement of accessory organs

Development of breasts

Appearance of axillary and pubic hair

Increased deposits of fat beneath the skin in general, particularly the hips and breasts

Widening and lightening of pelvis

Onset of menses