Lecture 14 Outline Reproductive System I
I. Functions of the Reproductive System
1. Secretion of sex hormones
2. Produces, transports, and nourishes sex cells-gametes
i. Male gamete = sperm
ii. Female gamete = oocyte (egg cell)
II. Meiosis
1. Specialized cell division that produces haploid gametes from diploid cells
i. Diploid cell = 2 full sets of chromosomes – 46 total
1. 23 paternal chromosomes from dad
2. 23 maternal chromosomes from mom
a. Maternal & paternal = homologous pairs
ii. Haploid = 1 full set of chromosomes – 23 total
1. Mix of paternal & maternal
2. DNA replication occurs prior to meiosis
i. Individual chromosomes produce copies
ii. Sister chromatids attached by a centromere (still called a chromosome)
3. Meiosis I = Separates homologous chromosomes
i. Prophase I
1. Nuclear envelope dissolves
2. Chromatin condenses into chromosomes
3. Synapsis = homologous chromosomes pair together
a. Crossing over may occur – adds genetic variation
4. Spindle fibers form
ii. Metaphase I
1. Homologous chromosomes line up along equatorial plate
2. Spindle fibers attach to centromeres
iii. Anaphase I
1. Spindle fibers contract
2. Homologous chromosomes separate
iv. Telophase I
1. Chromosomes reach opposite poles
2. Nuclear envelope reforms
3. Cytokinesis
4. Cells are now haploid (1 set of chromosomes)
4. Meiosis II
i. Prophase II
1. Chromatin condenses into Chromosomes
2. Nuclear envelope dissolves
3. Spindle fibers reform
ii. Metaphase II
1. Chromosomes line up along equatorial plate
2. Spindle fibers attach to centromeres
iii. Anaphase II
1. Spindle fibers contract
2. Sister chromatids separate
iv. Telophase II
1. Nuclear envelope forms
2. Cytokinesis
3. 4 haploid gametes from 1 diploid cell
Male Reproductive Anatomy
Testes = primary sex organs (gonads)
I. Function
1. Produce sperm
2. Secretes testosterone
II. Location
1. Within scrotum (skin pouch) outside abdominal wall
III. Development
1. Testes develop near kidneys in fetus
2. Testes descend through inguinal canal into scrotum before birth
i. Inguinal canals = weakness in abdominal wall, common site of hernias in males
3. Cryptoorchidism
i. Failure of testes descent
ii. Body temp = 37⁰C, but sperm develop at 34⁰C; results in infertility
IV. Structure
1. Tunica Albuginea – connective tissue capsule
2. Septa – connective tissue partitions
3. Lobule = space between septa
i. About 250 lobules per testis
ii. 1-4 seminiferous tubules per lobule
4. Seminiferous tubule = site of sperm production
5. Rete testis
i. tubule network, where seminiferous tubules converge
ii. Leads to epididymis = coiled tubule where sperm mature
Lecture 15 Outline Reproductive System II
Testes
I. Histology
1. Spermatogenic Cells
i. Gives rise to sperm cells
ii. Located within seminiferous tubules
1. Spermatogonia
· Undifferentiated spermatogenic cells
· Located adjacent to basement membrane
2. Spermatocytes
· Undergoing meiosis
3. Sperm
· Immature in lumen
· DNA in nucleus
· Mitochondria in body
· Tail = flagellum
iii. Sertoli Cells
1. Columnar epithelium
2. Nourish spermatogenic cells
3. Forms the blood-testis barrier = protection from immune system
2. Interstitial cells
i. Located between seminiferous tubules
ii. Secretes testosterone
Hormone regulation of testes
I. Anterior Pituitary Gland
a. Follicle stimulating Hormone (FSH)
i. Promotes sperm production from spermatogenic cells within seminiferous tubules
b. Luteinizing Hormone (LH)
i. Stimulates testosterone secretion from interstitial cells
II. Actions of testosterone
a. Stimulates enlargement of testes
b. Develops secondary sex characteristics
i. Increased body & facial hair
ii. Thickened skin
iii. Increases muscle mass
iv. Bone growth
v. Enlarges larynx
Epididymis “upon testis”
1. 18 foot coiled tube
2. Pseudostratified columnar epithelium
i. Nourishes sperm & promotes sperm maturation
1. Sperm taken from head of epididymis cannot fertilize an egg
2. Sperm taken from tail of epididymis can fertilize an egg
Vas Deferins
1. Muscular tube
2. Lined with pseudostratified columnar epithelium
3. Enters abdominal cavity within spermatic cord
Spermatic Cord
Conveys the following structures through inguinal canal:
1. Vas deferens
2. Testicular arteries & veins
3. Nerves
4. Cremaster muscle – contracts during cold to draw testes towards abdominal wall
Seminal Glands-secretes seminal fluid
1. Seminal Vesicles
· Secretes 60% of seminal fluid
· Fructose = energy for sperm
· Prostaglandins = stimulates muscle contractions of female reproductive tract
2. Prostate gland
· Thin milky fluid
· Alkaline = protects sperm against acidic environment
· Enhances motility of sperm
3. Bulbourethral gland
· Within urogenital diaphragm (contracts urethra)
i. Mucus-like fluid, luburicates tip of penis & urethra
Semen
1. Sperm cells + Seminal Fluid
a. Volume Released = 2-5mL
b. Average count = 120 sperm per mL
c. <13.5 million per mL = infertility
d. Sperm live up to 6 days after release, but can only fertilized in the first 48 hours
Penis
1. 3 columns of erectile tissue
a. Paired corpora cavernosum
i. Deep arteries
b. Single Corpus spongiosum
i. Urethra
ii. Enlarges at distal end to become glans penis
2. Erection
a. Parasympathetic stimulation promotes Nitric oxide release
b. Nitric Oxide = vasodilator
i. Arteries dilate,
ii. Veins become blocked
iii. Penis swells
Female Reproductive Anatomy
I. Overview
a. Gonads = 2 ovaries
b. Accessory Organs
i. 2 Uterine (fallopian) tubes
ii. 1 uterus
iii. Vagina
iv. Vulva = external genitalia
v. Mammary glands
II. Ligaments
a. Ovarian Ligaments
· anchors ovary to uterus
b. Suspensory Ligaments
· Attach ovaries to abdominal wall
· Contains ovarian arteries, veins, and nerves
c. Broad Ligaments
· Attaches uterus to abdominal walls
III. Ovary
a. Size & Shape of almond
b. Structure
i. Tunica albuginea = connective tissue capsule
ii. Ovarian epithelium
1. 85% of ovarian cancers are from ovarian epithelium
iii. Medulla
1. Loose connective tissue = stroma
2. Blood vessels, nerves, lymphatic vessels
iv. Cortex
1. Compact connective tissue
2. Ovarian follicles
a. Oocytes + granulosa cells
i. Follicles produced
1. Before birth = 5 million oogonia
2. At birth = 1million primary oocytes (meiosis I halts at birth)
3. At puberty = 400,000 primary oocytes
4. 12 reproductive cycles per year X 40 years = 480 oocytes released in a lifetime
IV. Oogenesis
a. Oogonium = diploid precursor
i. Mitosis
b. Primary Oocyte = diploid sex cell
i. Meosis I
1. Stalls at birth until puberty
c. Secondary Oocyte
i. 1 secondary oocyte + 1 polar body
ii. Hapoid sex cell
iii. Secondary oocyte consumes all cytoplasm from primary oocyte
iv. Polar body degenerates
v. Secondary oocyte ovulated from ovary
vi. Meiosis II
1. Secondary oocyte only undergoes meiosis II if fertilized by a sperm
2. 1 Ovum + 1 polar body
3. Fertilized ovum becomes zygote (diploid cell)
V. Follicle Maturation
a. Primordial Follicle
i. All primordial follicles are present at birth
ii. Primordial follicle = primary oocyte + flattened granulosa cells
b. Primary Follicle
i. 15-20 form per each reproductive cycle beginning at puberty
ii. Primary follicle =
1. Enlarged primary oocyte
2. Thickened layer of granulosa cells
c. Secondary follicle
i. Secondary oocyte
ii. 2 layers of granulosa cells
1. Corona radiate – adheres to secondary oocyte
2. Thecal layer
a. Theca interna = secretes steroid sex hormones
b. Theca externa = connective tissue
iii. Antrum
1. Fluid-filled cavity
2. Separates thecal layer from secondary oocyte
d. Mature follicle
i. 1 follicle persists & matures, the rest die off
e. Ovulation
i. Triggered by surge in Luteinizing hormone
ii. Releases Secondary oocyte + corona radiata into infundibulum of uterine tube
1. Corona radiata nourishes secondary oocyte
f. Corpus Luteum
i. Thecal layer remains intact in ovary after ovulation
ii. Develops into Corpus Luteum (yellow body)
1. Corpus luteum secretes progesterone
2. Progesterone maintains uterine wall during pregnancy
g. Corpus albicans
i. If pregnancy does not take place, corpus luteum degenerates
ii. Corpus albicans “white body” – remnants of corpus luteum
VI. Uterine Tube
a. Ciliated pseudostratified columnar epithelium + cilia + goblet cells
i. Cilia convey egg cell towards uterus
ii. Fertilization usually occurs in uterine tube
iii. Disorders
1. Ectopic pregnancy – implantation occurs outside of uterus
2. Tubular pregnancy
a. Implantation occurs in uterine tube
b. Uterine wall ruptures as embryo develops
c. Painful & serious condition
VII. Uterus
a. Structures
i. Fundus = belly
ii. Body
iii. Cervix = neck
b. Layers
i. Perimetrium
1. Serous membrane
2. Lubricates uterus
ii. Myometrium = large mass of smooth muscle
iii. Endometrium
1. Columnar epithelium
2. Blood vessels
3. Glands
4. Sloths off with each reproductive cycle
VIII. Vagina
a. Fibromuscular tube
b. Receives penis during sexual intercourse
c. Birth canal
d. 3 Layers
i. Inner = mucosal layer
1. Vaginal rugae = ridges
2. Stratified squamous epithelium
3. Mucous glands near cervix & vulva
ii. Middle = muscular layer
1. Smooth muscle
iii. Outer = fibrous layer
1. Dense connective tissue
2. Attaches vagina to surrounding organs
IX. Vulva “external genitalia”
a. Mons pubis
i. Fat pad
ii. Superficial to pubic symphysis
b. Labia majora
i. Folds of adipose
ii. Covered by skin & hairs
c. Labia minora
i. Stratified squamous epithelium
ii. Highly vascular = pinkish color
d. Vestibule = space between labia minora
i. Clitoris
1. Erectile tissue
2. Corresponds to male’s penis
ii. Urethral orifice
iii. Vaginal orifice
iv. Vestibular glands
1. Mucus-like secretions
2. Ducts open to vestibule
e. Perineum
i. Between pubic symphysis & coccyx
X. Hormonal Control of ovaries
a. Follicle Stimulating Hormone (FSH)
i. Promotes development of follicles
ii. Stimulates the conversion of androgens (secreted by granulosa cells) into estrogen
b. Luteinizing hormone (LH)
i. Stimulates the secretion of androgens from granulosa cells of follicles
ii. Triggers ovulation