24.0, 25.0 FEMALE REPRODUCTION

Reproduction III: Ovary

:

a)Define and use properly the following words:Ovary, Oogenesis, Cortex, Medulla, Hilum, Germinal epithelium, Tunica albuginea, Rete ovarii, Follicular development , Primordial germ cells, Primary oocytes, Oocytes arrested, Meiosis, Primordial follicles, Primary follicles, Follicular epithelium, zona pellucida, Secondary follicles, Oocyte, Granulosa cell, Thecal layers, Follicular antrum, Graafian follicle (tertiary follicle), Ovulation, Corpora hemorrhagicum, Corpus luteum, thecal lutein, granulosa lutein, Involution (luteolysis).

b)Describe and associate basic structure/function for the following: 1) all structures listed above; 2) changes that accompany maturation of a primordial follicle into a Graafian follicle.

c)Identify by microscopy: Corpora hemorrhagicum, Corpus luteum, Cortex, Follicular antrum, Follicular epithelium, Germinal epithelium, glycoprotein, Graafian follicle, Granulosa cell, Hilum, Involution, Medulla, Oocyte, Ovary, Ovulation, Primary follicle, Primordial follicle, Secondary follicle, Tertiary follicle, Theca, Tunica albuginea, Zona pellucida.

Reproduction IV: Female tract and Mammary Gland

Upon completion of this lecture, students will be able to:

a)Define and use properly the following words: Oviduct, Infundibulum, Ampulla, Isthmus, Pseudostratified, Ciliated cells, Sperm transport, Fertilization, Uterus, Endometrium, Myometrium, Perimetrium, Serosa, Uterine cycle, Anestrous, Estrous, Uterine cervix, Keratinized, Vagina, Mammary glands, Tubuloalveolar glands, Alveoli, Congealed milk.

b)Describe and associate basic structure/function for the following: 1) all structures listed above; 2) uterine endometrium and the role of hormones in the function of this organ; important features of the vagina and explain how they change during the reproductive cycle.

c)Identify by microscopy: Alveoli, Ampulla, Cilia, Congealed milk, Endometrium, Inactive mammary gland, Infundibulum, Isthmus, Keratinized, Lymphocytes, Mammary gland, Muscularis, Myometrium, Neutrophils, Oviduct, Perimetrium, Serosa, Stratified squamous epithelium, Tubuloalveolar glands, Uterine Cervix, Uterine glands, Uterus, Vagina.

FEMALE REPRODUCTION-OVARY

I.Functions:

  1. Oogenesis: Process of production of female gametes
  2. Reception of the male gametes the spermatozoa
  3. Provision of suitable environment for the fertilization of ova by spermatozoa
  4. Expulsion of the newborn to the external environment
  5. Nutrition of the newborn

II.Anatomy

  1. Attached to the posterior of the broad ligament by the mesovarium.
  2. Regions of the ovary
  3. Cortex (outer)
  4. Egg development in most animals except equine occurs here.
  5. Also the site of corpus luteum
  6. Medulla (center).
  7. In most animals the medulla includes the supporting functions for the ovary (blood vessels and lymphatics are found here).
  8. In equine egg development will occur in the medulla of the ovary, and the cortical region will contain the blood vessels, etc.
  9. The egg will then exit by way of the ovulation fossa.
  10. Hilum.
  11. Nerves, blood vessels, and lymphatics transverse the mesovarium, penetrate the ovary.

III.Histology

  1. Germinal epithelium
  2. Low cuboidal epithelium found on the outside of the ovary.
  3. Originally thought germ cells were produced here; not true.
  4. Tunica albuginea
  5. Present in some species.
  6. Prominent in the dog.
  7. In some species may only see remnants of it
  8. It is a CT layer of dense fibrous CT.
  1. Cortex
  2. It is located below the tunica albuginea.
  3. The cortex consists of follicles and a CT matrix between the follicles (ovarian stroma).
  4. Will also find corpus luteum and corpus albicans (you can ignore the corpus albicans for our purposes).
  5. No clear demarcation where the cortex ends and the medulla begins.
  1. Medulla
  2. Inner region
  3. Contains nerves, blood vessels, lymph vessels, connective tissue
  4. Rete ovarii
  5. Left over from the rete testis
  6. Near hilus
  7. Participates in regulating germ cells entering meiosis

IV.Follicular DEVELOPMENT

  1. Fetal
  2. Primordial germ cells migrate to cortex
  3. Divide by mitosis
  4. Primary oocytes
  5. ~500,000 (species dependent)
  6. Birth
  7. Oocytes arrested in meiosis
  8. Female germ cell number fixed at birth
  1. Adult
  2. Primordial follicles
  3. Single layer of flattened, squamous follicular cells that surround the oocyte.
  4. Primordial follicles can be found in nests or groupings of 10-20.
  5. Begin to mature together, but only one reaches full maturity and ovulates
  6. The primordial follicles are the smallest follicles.
  1. Primary follicles
  2. About 3x larger than the primordial follicles; less numerous.
  3. The oocyte will increase in size from that found in the primordial follicle.
  4. The main changes in size are due to the follicular epithelium.
  5. The follicular epithelium will be cuboidal in the primary follicle.
  6. The zona pellucida (which is a glycoprotein layer around the oocyte) starts to form, but it is not clearly present in the primary follicle.
  1. Secondary follicles
  2. Characterized by changes in the oocyte.
  3. The oocyte will now be maximal in size; larger than the primary follicle.
  4. One will also see prominent changes in the supporting cells.
  5. The supporting cells are now called granulosa cells.
  6. The granulosa cells will be stratified
  7. The zona pellucida is now formed and will be prominent.
  8. It is a glycoprotein layer around the oocyte.
  9. Stains pale pink in most preparations
  10. Thecal layers are the CT stroma around the follicle.
  11. There will be a basement membrane between the granulosa and thecal layers.
  12. You will not have to differentiate the thecal (interna and externa) layers, but you should be able to recognize and identify the thecal layer as a whole
  13. Fluid secretion by the granulosa cells will start but it will not form a follicular antrum until the tertiary follicle stage.
  1. Graafian follicle (tertiary follicle)
  2. The main way to identify it is look for the follicular antrum.
  3. The follicular antrum is an accumulation of fluid.
  4. The follicular fluid (liquor folliculi) is produced by granulosa cells
  5. There will also be a prominent zona pellucida.
  6. The tertiary follicle will be the largest in size; due to the:
  7. Follicle antrum
  8. Granules and thecal layers.
  9. The Graafian follicle is the fully mature and ready to be ovulated tertiary follicle, but for our purposes you can use the terms tertiary and Graafian follicle interchangeably.

V.Ovulation

  1. At the time of ovulation the oocyte and attached granulosa cells are released.
  2. The granulosa and thecal layers will remain.
  3. The follicle will collapse down because of the loss of the fluid.
  4. Since there is tissue damage, blood will collect in the antrum
  5. This will result in the corpora hemorrhagicum.
  6. It is rare to see the corpora hemorrhagicum because it is a transient structure.
  7. The corpus luteum will eventually develop from the granulosa and thecal layers.
  8. It will have an endocrine function.
  9. It consists of the thecal lutein and granulosa lutein cells (derived from the thecal and granulosa cells, respectively)
  10. You will not have to differentiate thecal lutein from granulosa lutein cells, but should be able to identify the corpus luteum, know what it produces, its fate, etc.

VI.Corpus Luteum

  1. Formation and structure
  2. It is formed from the granulosa and thecal layers.
  3. It consists of very large cells.
  4. These cells will produce steroids (progesterone).
  5. Thus, these cells will have an abundance of SER and Golgi apparatus.
  6. It will be a transitory organ.
  7. If pregnancy occurs, then the CL will be maintained throughout gestation.
  8. In some species the CL is only needed in the beginning of gestation.
  9. Its function will be taken over by the fetal placenta.
  1. Involution (luteolysis)
  2. If pregnancy doesn't occur, the CL will die.

VII. Species Variations

  1. In the equine, the follicles develop in the medulla.
  2. During ovulation, the egg will be released into the ovulation fossa.

FEMALE REPRODUCTION-TRACT

I.Anatomy

  1. Oviduct
  2. Uterus
  1. Vagina
  2. Mammary glands

II.Female Reproductive Tract Shows Marked Species Differences

The organ that is least variable is the ovary, but the uterus, vagina, cervix, etc. show marked species variations

III.Regions of the Oviduct

Infundibulum

Ampulla

Isthmus

IV.Oviduct

  1. It consists of a highly folded mucosa (this will show a lot of variation throughout its length).
  2. The mucosa will consist of a CT core and an outer epithelium.
  3. The epithelium will be simple columnar (pseudostratified in the sow and cow).
  4. some of the cells will have cilia (real, motile cilia).
  5. Estrogens and progesterone will affect the height and presence of cilia on the epithelium.
  6. The oviductal mucosa is surrounded by smooth muscle.
  7. The histology of the oviduct will vary with species, region (the # of ciliated cells increases as you move toward the uterus, while the height of the mucosal folds decreases), and presence or absence of hormones.
  1. Functions of the Oviduct
  2. Helps to transport the egg after ovulation.
  3. Facilitates sperm transport.
  4. It can be the site of fertilization.
  5. It has a role in nurturing the egg in that it will produce a mucus secretion for the oocyte.

V.UTERUS

  1. Endometrium
  2. Epithelium
  3. Luminal is simple columnar.
  4. In the dog blind ending crypts of luminal epithelium will also be present.
  5. Glandular is found within the CT stroma, and it is derived from the luminal epithelium.
  6. A stromal layer, consisting of CT, which contains vascular elements.
  7. Myometrium
  8. Very thick muscle layer consisting of smooth muscle fibers arranged in different histological orientations.
  9. The uterus is in essence a very muscular tube.
  1. Perimetrium
  2. Serosa covering the myometrium.
  1. Cyclic changes in the uterus.
  2. Hormones from the ovary (estrogens and progesterone) will control the height, activity of the uterine epithelium.
  3. If remove the ovary, the epithelium will go from columnar to cuboidal (the epithelial cells are less active).

VI. Uterine Cervix

  1. Epithelium
  2. In some species resembles the vaginal epithelium
  3. stratified squamous epithelium
  4. In some species the cervical epithelium is keratinized, while in other species it is not be keratinized.
  5. Cyclical changes
  6. The height and keratinization of the epithelium is hormone dependent.
  7. Estrogen and progesterone are the major hormones controlling cervical epithelial histology.
  8. Function
  9. The cervix separates the vagina from the uterus; site of semen deposition in some species
  10. It will form a protective barrier against pathogens.
  11. It will also prevent sperm from entering the uterus during anestrus.

VII. Vagina

  1. Histological structure.
  2. Stratified squamous epithelium.
  3. In some animals (e.g., rat, mouse, opossum) it will also be keratinized.
  4. In other animals (e.g., dog) it will never be keratinized.
  5. Basal layer of the epithelium is the site of cell proliferation;
  6. cells above the basal layer are post-mitotic
  7. Loose CT supporting epithelium is less cellular than in the uterus.
  8. Muscularis layer.
  9. It is relatively thick and it is composed of smooth muscle (but much thinner than the smooth muscle layer seen in the uterus!!).
  10. Cyclical changes during the reproductive cycle.
  11. The morphology of the vagina will vary with the stage of estrous
  12. Few layers during anestrous; many during estrous
  1. Hormonal regulation of vaginal differentiation, growth, and function.
  2. Estrogens will cause an increase in height of the epithelium and in some animals (not the dog) estrogens will also increase the keratinization.
  3. Progesterone also affects vaginal histology

VIII. Mammary Glands

  1. Function
  2. A system to nourish the developing young.
  3. Similar to sweat glands
  1. Development of the mammary glands
  2. Prepubertal
  3. Atrophic; not developed.
  4. Puberty in females
  5. Development increases during puberty,
  6. but the glands are still not functional (not capable of producing milk);
  7. Pubertal development is hormone dependent.
  8. Until the glands become active mostly CT and fat are found within the tissue.
  9. Active glands
  10. prolactin and oxytocin
  11. The hormones responsible for milk production and milk letdown (ejection)
  1. Histology of active mammary glands
  2. Tubuloalveolar glands.
  3. Alveoli are the secretory unit of the gland.
  4. Lined by cuboidal to columnar epithelium.
  5. Within the epithelium one will see vacuolations
  6. represents the lipid that was washed out in processing
  7. In the lumen of the tubules one will see
  8. Congealed milk
  9. Cells (lymphocytes along with as few mammary epithelial cells)
  10. Composition of the milk and control of milk letdown
  11. Milk is composed of water, lipid, proteins, and lymphocytes (Ig).
  1. Postlactational regression
  2. After lactation has ceased, the mammary gland will regress
  3. The inactive mammary gland will be composed of CT and fat with little glandular tissue.