1. Anatomy of the Reproductive System
Lab Activity 33
Anatomy of the
Reproductive System
Portland Community College
BI 233

2. Scrotum
Sac of skin and superficial fascia that hangs outside the abdominopelvic cavity at the root of the penis
Contains paired testicles separated by a midline septum
Its external positioning keeps the testes 3C lower than core body temperature

3. Penis
Internal penis: The urethra and three cylindrical bodies of erectile tissue
Corpus spongiosum: Surrounds the urethra and expands to form the glans and bulb of the penis
Corpora cavernosa: Paired dorsal erectile bodies bound by fibrous tunica albuginea
Crura: anchors the penis to the pubic arch

6. Penis Histology

7. Testicles Seminiferous tubules:
Produce the sperm
Converge to form the tubulus rectus
The straight tubulus rectus conveys sperm to the rete testis
From the rete testis, the sperm:
Leave the testis via efferent ductules
Enter the epididymis
Surrounding the seminiferous tubules are interstitial cells

8. Testicle

9. Seminiferous Tubules “Sperm Factory”
Interstitial cells (Leydig cells)
In the soft connective tissue surrounding the seminiferous tubules.
Produce Testosterone when stimulated by LH

10. Seminiferous Tubules “Sperm Factory”
Sertoli Cells (sustentacular cells)
Support and nourish the spermatogenic cells
Completely surround the spermatic cells undergoing meiosis
Creates the blood-testes barrier
Stimulated by FSH
Secretes:
Androgen binding protein (ABP): Concentrates testosterone in the seminiferous tubules
Inhibin: Released when sperm production is too high (slows it down). Inhibits the secretion of FSH and GnRH

12. Seminiferous Tubules

13. Seminiferous Tubules Histology

14. Epididymis Epididymis: Storage and maturation area for sperm
Its head joins the efferent ductules and caps the superior aspect of the testis
The duct of the epididymis has stereocilia that:
Absorb testicular fluid
Pass nutrients to the sperm
Nonmotile sperm enter, pass through its tubes and become motile (propelled by peristalsis)
Upon ejaculation the epididymis contracts, expelling sperm into the ductus deferens

15. Ductus Deferens and Ejaculatory Duct
Ductus Deferens: Runs from the epididymis through the inguinal canal into the pelvic cavity
Ampulla: The expanded terminal end on posterior bladder
Ejaculatory Duct: Formed from the ampulla and the duct of the seminal vesicle
Most of it is in the prostate gland
Propels sperm from the epididymis to the urethra

16. Ampulla
Seminal vesicle
Ejaculatory Duct

17. Spermatic Cord
Contains the structures running from the testicles to the pelvic cavity.
Passes through the inguinal canal
Contents:
Vas Deferens
Nerves
Blood Vessels

18. Accessory Glands: Seminal Vesicles
Lie on the posterior wall of the bladder and secrete 60% of the volume of semen
Seminal fluid:
Fructose: provides energy for the sperm.
Fibrinogen: helps turn semen into a bolus that can be readily propelled into the vagina.
Prostaglandins: decrease cervical mucus viscosity and stimulate reverse peristalsis of the uterus.
Join the ductus deferens to form the ejaculatory duct

19. Posterior Bladder

20. Accessory Glands: Prostate Gland
Doughnut-shaped gland that encircles part of the urethra inferior to the bladder
Plays a role in the activation of sperm
Enters the prostatic urethra during ejaculation
Prostatic secretions include:
Citrate: is a food source (TCA cycle)
Proteolytic enzymes: acts to "decoagulate" the semen that was coagulated by seminal vesicle secretions, which helps the sperm begin their journey once inside the vagina

21. Bulbourethral Glands (Cowper’s Glands)
Pea-sized glands inferior to the prostate
Produce alkaline mucus prior to ejaculation that neutralizes traces of acidic urine in the urethra

22. Sperm Summary Produced: Seminiferous tubules Stored: Epididymis
Transported through epididymis by rhythmic peristaltic contractions as they mature
Epididymis Vas Deferens  Ejaculatory duct (ampulla of vas deferens fuses with duct of seminal vesicle “ejaculatory duct”)  prostate prostatic urethra (then passes the bulbourethral gland) membranous urethra  penile urethra

23. Female External Genitalia
Mons pubis: fatty pad over the pubic symphysis
Labia majora & minora: folds of skin encircling vestibule where find urethral and vaginal openings
Clitoris: small mass of erectile tissue
Bulb of vestibule: masses of erectile tissue just deep to the labia on either side of the vaginal orifice
Perineum: Area between the vagina and anus

24. Female External Genitalia
Perineum

25. Vagina
Thin-walled tube lying between the bladder and the rectum, extending from the cervix to the exterior of the body
Wall consists of three coats: fibroelastic adventitia, smooth muscle muscularis, and a stratified squamous mucosa
Mucosa near the vaginal orifice forms an incomplete partition called the hymen
Vaginal fornix: upper end of the vagina surrounding the cervix

26. Bartholin’s Glands (aka: Vestibular Glands)
The Bartholin's glands are located on each side of the vaginal opening.
They secrete fluid that helps lubricate the vagina.
Sometimes the ducts of these glands become obstructed.
Fluid backs up into the gland and causes swelling (Bartholin's cyst)

27. Female: Lateral View

28. Cervix
Narrow lower neck of the uterus which projects into the vagina inferiorly
Cervical canal – cavity of the cervix that communicates with:
The vagina via the external os
The uterine body via the internal os
Cervical glands secrete mucus that covers the external os and blocks sperm entry except during midcycle

29. Endocervical canal
Fornix

30. Uterine Tubes (Fallopian Tubes)
Receive the ovulated oocyte and provide a site for fertilization
Empty into the superolateral region of the uterus via the isthmus
Expand distally around the ovary forming the ampulla
The ampulla ends in the funnel-shaped, ciliated infundibulum containing fingerlike projections called fimbriae

31. Uterine Tubes (Fallopian Tubes)
Function: events occurring in the uterine tube
Fimbriae sweep oocyte into tube, cilia & peristalsis move it along, sperm reaches oocyte in ampulla, fertilization occurs within 24 hours after ovulation & zygote reaches uterus about 7 days after ovulation

32. Fallopian Tube Histology
Cilia sweep egg/zygote toward the uterus

33. Uterus
Hollow, thick-walled organ located in the pelvis anterior to the rectum and posterosuperior to the bladder
Body: Major portion of the uterus
Fundus: Rounded region superior to the entrance of the uterine tubes
Isthmus: Narrowed region between the body and cervix

34. Uterus

35. Uterine Histology Endometrium Simple columnar epithelium
Stroma of connective tissue and endometrial glands
Stratum functionalis: Shed during menstruation
Stratum basalis: Replaces stratum functionalis each month
Myometrium
3 layers of smooth muscle
Perimetrium
Visceral peritoneum

36. Uterine Histology

37. Endometrium
Simple columnar epithelium
Endometrial glands

38. Ovaries Each follicle consists of an immature egg called an oocyte
Cells around the oocyte are called:
Follicle cells (one cell layer thick)
Stimulated to mature by FSH from the pituitary gland
Granulosa cells (when more than one layer is present)
Thecal cells: Cells in the ovarian stroma
Thecal & granulosa cells work together to produce estrogen

39. Follicle Development
Primordial follicle: one layer of squamous-like follicle cells surrounds the oocyte
Primary follicle: two or more layers of cuboidal granulosa cells enclose the oocyte
Secondary follicle: has a fluid-filled space between granulosa cells that coalesces to form a central antrum
Graafian follicle: secondary follicle at its most mature stage that bulges from the surface of the ovary
Corpus luteum : ruptured follicle after ovulation

40. Ovary Histology

41. Ovary Histology

42. Primary Follicle 1° Oocyte (arrested in prophase I) Nucleus
Primordial follicle
Zona pellucida
Thecal cells
Granulosa cells

43. Secondary Follicle

44. Graafian Follicle Fluid filled antrum Oocyte 2° Granulosa cells Stalk
Corona radiata
Zona pellucida

45. Ovulation
LH from the pituitary gland will cause the Graafian follicle to rupture
The oocyte will be released (ovulation)
The follicle is now a corpus luteum
Secretes estrogen and progesterone

46. Mammary Glands Modified sweat glands that produce milk (lactation)
Amount of adipose determines size of breast
Milk-secreting glands open by lactiferous ducts at the nipple
Areola is pigmented area around nipple
Suspensory ligaments suspend breast from deep fascia of pectoral muscles (aging & Cooper’s droop)

47. Breast

48. Breast
Prolactin from the pituitary gland stimulates the synthesis of milk
Oxytocin from the posterior pituitary gland stimulates milk ejection

49. Lymphatic Drainage
Lymph nodes draining the breast are located in the axilla.

50. Lab Activity 34
Gametogenesis

51. Gametogenesis
Each cell has two sets of chromosomes (one maternal, one paternal) and is said to be diploid (2n chromosomal number)
Humans have 23 pairs of homologous chromosomes
Gametes only have 23 chromosomes and are said to be haploid (n chromosomal number)
Gamete formation is by meiosis, in which the number of chromosomes is halved (from 2n to n)

53. Review of Mitosis
DNA replication happens during interphase and is not part of mitosis (or meiosis)
Mitosis (and then cytokinesis)
Results in the formation of two daughter cells identical to the original cells
Prophase
Metaphase
Anaphase
Telophase

54. Mitosis
Original cell
Cell with replicated DNA just prior to starting mitosis (X represents sister chromatids: 2 copies of the same chromosome)
Daughter cells

55. Prophase
First part of cell division
Centromeres migrate to the poles

56. Metaphase
Sister chromatids align in the center of the cell along the spindle that radiates from the centromeres

57. Anaphase
Sister chromatids are pulled toward the poles so that each new cell will get only one copy of the chromosome
The cell begins to elongate

58. Telophase Daughter nuclei begin forming
A cleavage furrow (for cell division) begins to form

59. Meiosis DNA replication happens during interphase
Meiosis consists of two nuclear and cellular divisions.
The first division is known as meiosis I and results in two haploid cells.
During meiosis II, those two haploid cells divide, yielding a total of four haploid cells.

60. Meiosis I Meiosis II Original cell
Cell with replicated DNA just prior to starting meiosis
Cells at the end of meiosis I (sister chromatids stay together)

61. Prophase I: Synapsis
Homologous pairs of chromosomes undergo synapsis and form tetrads with their homologous partners (4 chromosomes)
Crossover: Genetic material is exchanged between the homologous chromosomes.
Parts of maternal chromosomes may be exchanged with paternal ones
Genetic recombination produces gametes unlike either parent

62. Exchange of Genetic Material
Genes are exchanged between homologous chromosomes

63. Meiosis I Metaphase I: Tetrads line up at the spindle equator
Anaphase I: Homologous chromosomes (still composed of joined sister chromatids) are distributed to opposite ends of the cell
Telophase I: The nuclear membranes re-form around the chromosomal masses
Cytokinesis: The cytoplasm is split in two.

65. Results of Meiosis I At the end of meiosis I each daughter cell has:
Two copies of either a maternal or paternal chromosome
(Compare to mitosis where you get one copy of maternal and one copy of paternal)
A 2n amount of DNA and haploid number of chromosomes

66. Meiosis II
Mirrors mitosis except that chromosomes are not replicated before it begins
Meiosis II accomplishes two tasks:
It reduces the chromosome number by half
(2n to n)
Each of the daughter cells produced by meiosis I divides during meiosis II and the net result is 4 genetically unique haploid cells or gametes.

68. Meiosis

69. Spermatogenesis
Spermatogenic stem cells of the seminiferous tubules give rise to sperm in a series of events
Mitosis of spermatogonia, forming spermatocytes
Meiosis forms spermatids from spermatocytes
Spermiogenesis: spermatids form sperm

70. Spermatogenesis

71. Spermiogenesis: Spermatids to Sperm

72. Sperm Sperm have three major regions
Head :contains DNA and has a helmet-like acrosome containing hydrolytic enzymes that allow the sperm to penetrate and enter the egg
Midpiece: contains mitochondria spiraled around the tail filaments
Tail :a typical flagellum produced by a centriole

73. Sperm

74. Oogenesis: Before birth
During fetal development, oogonia (stem cells) divide by mitosis to make primary oocytes
Primary oocytes begin meiosis and stop in prophase I until puberty
Primordial follicles: Support cells that surround the oocyte in the ovary
2 million present at birth
400,000 remain at puberty

75. Oogenesis: After Puberty
Each month, hormones cause several follicles to develop, which triggers the primary oocyte to resume meiosis I
Polar bodies: When the cell divides, all the cytoplasm and organelles stay with one of the new cells, the other cell is just DNA, and is called a polar body and is discarded
Secondary oocyte: The stage at which ovulation occurs.

76. Oogenesis: After Puberty
The secondary oocyte begins meiosis II, but stops in metaphase II
The secondary oocyte is ovulated
Meiosis II is completed only if it is fertilized.

77. Oogenesis

78. Life History of Oogonia
As a fetus, oogonia divide to produce millions by mitosis but most degenerate (atresia)
Some develop into primary oocytes & stop in prophase stage of meiosis I
200,000 to 2 million present at birth
40,000 remain at puberty but only 400 mature during a woman’s life
Each month, hormones cause meiosis I to resume in several follicles so that meiosis II is reached by ovulation
Penetration by the sperm causes the final stages of meiosis to occur

79. The End
The End