A&P Chapter 28: Reproductive system
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Where are interstitial (Leydig) cells found and what do they produce?
- 1. Seminiferous tubules of the testes
- 2. Produce androgens (testosterone)
What are the functions of nurse cells in the seminiferous tubules?
- 1. Support spermiogenesis
- 2. Maintain the blood-testes barrier
- 3. Secrete inhibin
- 4. Androgen binding protein
- 5. Müllerian inhibiting factor
- 6. Support mitosis and meosis
List the cellular transformation that happens during spermatogenesis
- 1. Mitosis of spermatogonium (stem cell) - 46 chromosomes, produces 1 spermatogonium and 1 primary spermatocyte
- 2. Meiosis - primary spermatocyte produces 2 secondary spermatocytes, meiosis II forms 4 spermatids (gamete) 23 chromosomes
- 3. Spermiogenesis - spermatids differentiate into spermatozoa with help of nurse cells
Describe the contents of semen
- 1. Spermatozoa: 20-100mil/mL
- 2. Seminal fluid: glandular secretions from seminal, prostate and bulbo-urethro glands
- 3. Enzymes:
- Protease to dissolve mucus in vagina
- Seminalplasmin to kill bacteria
- Enzyme to convert fibrinogen to fibrin
- Fibrinolysin to dissolve clotted semen
What is the role of FSH in males?
- 1. Stimulate the nurse cells:
- To promote spermatogenesis
- To secrete androgen binding protein
- To secrete inhibin
What are the male accessory glands and what are the contents of their secretions?
- 1. Seminal gland: fructose, protaglandins and fibrinogen
- 2. Prostate gland: seminalplasmin with antibiotic properties (slightly acidic)
- 3. bulbourethral glands: alkaline mucus to neutralize urinary acids and lubricate glans penis
What is the role of LH in males?
1. Targets the interstitial cells to produce testosterone and other androgens
What is the role of LH in females?
- Day 14: massive surge in LH triggers:
- 1. Completion of meiosis I
- 2. Rupture of the follicle wall
- 3. Ovulation
- 4. Formation of the corpus luteum
- 5. LH surge is triggered by increased GnRH pulse frequency and elevated estrogen levels
What is the role of FSH in females?
- 1. Follicle development
- 2. Secretion of inhibin from granulosa cells
- 3. Secretion of estrogen from granulosa cells
What are the 3 phases of the menstrual (uterine) cycle?
- 1. Days 1-6: Menses, degeneration of the functional zone of the endometrium
- 2. Days 7-14: Proliferative phase, restoration of the uterine epithelium through cell growth and vascularization
- 3. Days 15-28: Secretory phase, uterine glands enlarge and accelerate their rate of secretion, arteries spiral through the tissue
What hormones are active during the proliferative phase of the uterine cycle?
The proliferative phase is stimulated and sustained by estrogens secreted in the developing follicles
What hormones are active during the secretory phase of the uterine cycle?
- 1. Progestins and estrogens from the corpus luteum
- 2. The secretory phase begins at the time of ovulation and persists as long as the corpus luteum remains intact
What is the vulva and what are some of its components
- 1. Female external genitalia:
- Labia majora
- Labia minora
- Mons pubis
What are the 2 phases of the ovarian cycle?
- 1. Follicular phase: primordial follicle --> primary follicle --> secondary follicle --> tertiary follicle --> ovulation
- 2. Luteal phase: corpus luteum forms, stimulated by LH to maintain structure and function, secretes progesterone to prepare uterus for pregnancy
What hormones are active during the follicular phase of the ovarian cycle?
- 1. Begins with FSH stimulation
- 2. Androstenedione produced by thecal cells
- 3. Androstenedione is absorbed by granulosa cells and converted to estrogens
What are the 3 forms of estrogens?
- 1. Estradiol (most abundant)
- 2. Estrone
- 3. Estriol
What are the 5 general functions of estrogen?
- 1. Stimulate bone and muscle growth
- 2. Maintain female secondary sex characteristics (hair distribution and adipose tissue deposits)
- 3. Affects CNS activity (esp. hypothalamus where estrogens increase sexual drive)
- 4. Maintaining functional accessory reproductive glands and organs
- 5. Initiating the repair and regrowth of the endometrium
What are the main functions of testosterone?
- 1. Stimulates spermatogenesis
- 2. Affects CNS activity (libido and sexual behavior)
- 3. Stimulates protein synthesis, blood cell formation, muscle/bone tissue growth
- 4. Establishes male secondary sex characteristics
- 5. Maintains accessory reproductive glands and organs
- 6. Functions like other steroid hormones (lipid soluble, binds to DNA)
What hormones are involved during the luteal phase of the ovarian cycle?
- 1. Triggered by spike in LH
- 2. Progesterone levels rise
- 3. Estrogen levels fall
- 4. GnRH pulse frequency declines sharply which stimulates LH secretion
What are the 7 main steps of the ovarian cycle?
- 1. Primordial follicles in egg nest: single squamous layer of follicle cells surround each oocyte to form the primordial follicle
- 2. The formation of primary follicles: primordial follicles are activated into primary follicles, granulosa and thecal cells surround the follicle
- 3. The formation of secondary follicles: Wall of primary follicle thickens and secretes follicular fluid, this secondary follicle rapidly grows in size
- 4. The formation of a tertiary follicle: 2ndary follicle grows to become tertiary follicle (15mm diameter), oocyte completes meiosis I and metaphase of meiosis II
- 5. Ovulation: surge in LH causes the tertiary follicle releases the secondary oocyte by rupturing the follicular wall, ejected contents is moved into uterine tube by fimbriae
- 6. Formation of the corpus luteum: the granulosa cells remaining from the tertiary follicle make the corpus luteum, secretes progesterone to prepare uterus for pregnancy
- 7. Formation of the corpus albicans: degeneration of the corpus luteum, progesterone levels fall, fibroblasts invade
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