1. Welcome to Histology and Embryology: Unit 5 Seminar!
Please feel free to chat amongst yourselves
until we begin at the top of the hour.

2. Seminar Agenda
The Reproductive System
Questions & Answers

3. Unit 3-5 Project: Histology
NOTE:
Topic Choice, Outline and List of References are due at the end of Unit 3: 30 points
Complete Paper (Part 1; Histology) due at the end of Unit 5: 150 points
For the tissue or organ that you selected, you should:
Describe the histological characteristics of the tissue or organ.
Correlate the structural characteristics of the tissue with their function.
Discuss the importance of histological characteristics of the tissue or organ to the body function as a whole.

4. Unit 3-5 Project: Histology
Topic Proposal:
Topic Proposal: The topic should be on the histology of a tissue or organ of your choice.
In a properly formatted document submit your completed project, including a title page, body of the project write-up and the references you will use.
The title page should contain the title of the paper, your name and course details.
The body of the write-up should begin on page 2, and the references should start on a new page at the end of the essay. The text portion of your project should be between 5-7 pages long.
Your final project should be properly formatted to include subtitles if appropriate, written with Times New Roman, Arial or Calibri fonts, size 12 on letter-size paper with 1-inch margins.
The completed project must be uploaded to dropbox by the end of Unit 5.

5. Questions

6. Embryology -terminology

7. Gametogenesis Human development begins at fertilization
Male gamete (sperm) and female gamete (oocyte) come together and form a single cell or zygote.
Sperm and oocytes contain half the number of chromosomes (haploid number) than present in somatic (body) cells.
Gametogenesis is the process of formation and the development of specialized generative cells called gametes.

8. The stages of meiosis I and II
Let’s first label each stage.
Interphase
Prophase I
Metaphase I
Anaphase I
Prophase II
Metaphase II
Anaphase II
Telophase II
(and cytokinesis)
Telophase I
(and cytokinesis)

9. The Stages of Meiosis I Interphase Prophase I Metaphase I Anaphase I
The chromosomes replicate. It is similar to chromosome replication of mitosis. Two identical sister chromatids are held together by a centromere.
Chromosomes shorten and thicken. Each chromosome pairs with its corresponding homologous chromosome to form a tetrad. There are 4 chromatids in a tetrad.
Tetrads line up at the center of the cell.
The tetrads break apart and the pairs move to opposite sides of the cell. Sister chromatids remain attached at their centromeres.

10. The Stages of Meiosis II
Telophase I
(and cytokinesis)
The cell separates into two cells.
Prophase II
Metaphase II
Anaphase II
Telophase II
The pairs of sister chromatids start toward the center.
Pairs of sister chromatids line up at the center.
The pairs of sister chromatids separate and move to opposite sides of the cell.
(and cytokinesis)
Meiosis I results in 2 haploid (1N) daughter cells
Results in 4 new cells that are 1N.
Each daughter cell has half the number of chromosomes as the original cell.

11. The Importance of Meiosis
1 (2N) cell > 4 (1N) cells
The chromosome number of the egg and sperm is cut in half to insure that the zygote will have the proper number of chromosomes.

12. homologous chromosomes
“Crossing Over” During Meiosis
tetrad
This process is called “____________”
During ________, each pair of chromatids lines up next to its _________.
prophase I
crossing over
homologue
homologous chromosomes
This pairing of homologous chromosomes produces _______.
It is possible for the chromatids within a homologous pair to twist around one another. Portions of the chromatids may break off and attach to adjacent chromatids.
tetrads
“Crossing over” is the exchange of genetic information (genes) between segments of homologous chromosomes during meiosis.
A tetrad consists of
___________.
4 chromatids

13. Meiosis produces four haploid cells that are different.
Gamete
Formation
In males, meiosis results in 4 sperm cells.
In females, 4 cells are produced, but only one will become an egg cell. All of the cytoplasm and all of the organelles are put into one egg cell. The other three cells will never be functional.

14. Comparison of Mitosis and Meiosis
Mitosis occurs in all cells of the _____ except _____________.
Meiosis only occurs in the formation of _____________.
body
egg and sperm
egg and sperm

15. Diploid, 2N
Haploid, 2N
Haploid, 1N

16. Spermiogenesis

17. Oogenesis: Prenatal Maturation of Oocytes
Oogonia are transformed into mature oocytes.
Maturation process begins before birth and is completed after puberty.
Oogonia
- immature ovum
- proliferate during early fetal life
- oogonia enlarge to form primary oocytes before birth
Primary oocyte
- connective tissue cells surround it and form a single layer of flattened, follicular epithelial – primordial follicle
- zona pellucida forms – amorphous glycoprotein material that surrounds the primary oocyte
- begin the first meiotic division before birth, but completion of prophase does not occur until adolescence
- follicular cells secrete oocyte maturation inhibitor which keeps the meiotic process arrested

18. Oogenesis: Postnatal Maturation of Oocytes
During puberty, one follicle matures each month and ovulation occurs
Long duration of the first meiotic division of up to 45 years
may account in part for the relatively high frequency of meiotic errors in older females
Nondisjunction – failure of paired chromatids to dissociate
Primary oocyte in suspended prophase is vulnerable to environmental effects
No primary oocytes form after birth in females
Follicle maturation – primary oocyte increases in size and before ovulation completes the first meiotic division resulting in a secondary oocyte and first polar body
Polar body – small dysfunction cell that degenerates

19. Oogenesis:Postnatal Maturation of Oocytes (cont’d)
At ovulation –
Secondary oocyte begins second meiotic division, but progresses only to metaphase when division is arrested
Sperm penetration results in the completion of the second meiotic division
Results in fertilized oocyte and second polar body
There are approximately two million primary oocytes in the ovaries of newborn female
Most regress during childhood
Adolescence only have 40,000 primary oocytes
Only 400 become secondary oocytes and are expelled at ovulation during reproduction

20. Oogenesis

21. Male and female gametes

22. Abnormal Gametogenesis: chromosomal abnormalities

23. Nondisjunction

24. Trisomy 21

25. Uterus Uterus has three layers: Perimetrium Myometrium Endometrium
The functional layer of the endometrium is sloughed off during menstration

26. Ovarian cycle:
Follicle-stimulating hormone (FSH) stimulates the development of ovarian follicles and the production of estrogen by the follicular cells
Leuteinizing hormone (LH) serves as the “trigger” for ovulation (release of secondary oocyte) and stimulates the follicular cells and the corpus luteum to produce progesterone

27. Female Reproductive System
Ovaries
Form in a fetus under influence of X chromosome
Primordial germ cells, called oocytes, in outermost cortical region of ovary
Primordial follicle = small oocyte enclosed in a single layer of simple squamous cells derived from the surrounding ovarian connective tissue (stroma)
Cortical region has a layer of dense connective tissue called tunica albuginea and a layer of epithelium called the germinal epithelium
At puberty, oocytes and follicles enlarge due to the expression of gonadotropins
Small number develop into primary follicles

28. Female Reproductive System
Primary follicle
zona pellucida secreted by oocyte
cells outside zona pellucida round up and divide to form the cells of the granulosa layer

29. Primordial follicle (left) and secondary follicle (right)

30. Female Reproductive System
Secondary follicle
granulosa cells secrete large amounts of fluid called liquor folliculi that accumulates within a large space called an antrum
As the antrum enlarges the follicle become ready for ovulation – graafian follicle

31. Female Reproductive System

32. Female Reproductive System

33. Ovulation

34. Hormones during menstrual cycle

35. Fertilization

37. Blastocyst formation

38. Attachment of the blastocyst to the endometrial epithelium

39. First week

40. Questions