Bio Quiz 6

Describe three common nitrogenous waste forms utilized in different animals. Assess each according to relative toxicity, metabolic energy expenditure needed to produce it, and degree of water loss to excrete.

Ammonia, Urea, and Uric acid are the three common types of nitrogenous waste in animals. Ammonia has a high toxicity so it can not accumulate in tissue and it takes a lot of energy to metabolize. Also has to be excreted with high water loss. The next form of waste is urea and it is moderately toxic as it also cannot be allowed to accumulate in tissues. It requires metabolic energy to produce from ammonia and can be excreted in more concentration which reduces water loss. Lastly uric acid is relatively non-toxic and falls out of solution at low concentration. It requires significant metabolic energy to produce from ammonia and is excreted as solid which allows for minimal water loss

Key ideas:

• Ammonia

• High toxicity

• High energy to metabolize

• High water loss

• Urea

• Moderately  toxic

• Medium energy to metabolize

• Excreted in higher concentration, reducing water loss

• Uric acid

• Relatively non-toxic

• Significant metabolic energy

• Excreted as a solid for minimal water loss

Describe the path of excretory filtrate in the kidney, starting with Bowman’s capsule and ending in the renal pelvis. Describe the exchanges that occur in each tubule segment during movement through this path.

Starting in the Bowman’s capsule, filtration is driven by hydrostatic pressure of fluid in the glomerulus. As fluid passes through the proximal convoluted tubules, solutes are useful/needed solutes are reabsorbed through the tubule walls and into the peritubular capillaries. Waste is also moved into proximal convoluted tubules by secretion. Countercurrent exchanges occurring in the loop of henle serve to form a solute gradient in the interstitial fluid of the kidney, increasing in concentration from cortex to the medulla.

Describe the relative advantages of asexual and sexual reproduction.

• Asexual Reproduction 

- Allows for rapid population growth

- Only one parent is required for the process. Eliminates the need to find a mate, and conserves energy. 

- Offspring are adapted to the environment

• Sexual Reproduction

• Produces greater genetic diversity which allows populations to adapt, and survive to the presence of new challenges. 

• Increased genetic diversity also increases the range of defenses against pathogens and diseases. 

Describe the stages and path of sperm development and movement through the male reproductive system.

The beginning of sperm development starts with Spermatogonia. 

Spermatogonia are the germ cells that are housed in the testes.

 They undergo mitosis to produce more spermatogonia, or differentiate into primary spermatocytes.

 Primary Spermatocytes are diploid cells that undergo meiosis I to reduce their chromosome number by half, creating two haploid secondary spermatocytes. 

Secondary Spermatocytes are cells that undergo meiosis II, dividing to form spermatids, which are also haploid. 

Spermatids are immature sperm cells that undergo a transformation called spermiogenesis, where they develop a head, midpiece, and tail, becoming fully functional sperm. 

Spermatozoa: Are what spermatids develop/mature into. They are ready to be transported out of the testes. 

Mature sperm are transported into the epididymis ( long coiled tube attached to each testis ) where sperm undergo further maturation. Sperm gain the ability to swim and become more motile- therefore more capable of fertilizing an egg. 

Sperm are stored in the epididymis until ejaculation. They remain viable here for several weeks. 

Then sperm are transported from the epididymis through the vas deferens ( muscular tube that connects the epididymis to the ejaculatory ducts ). Sperm gets mixed with fluids produced by accessory glands: Seminal Vesicles - add fructose fluid that provides energy for sperm motility.

Prostate Gland: Secretes slightly acidic fluid that neutralizes the acidic environment of the vagina, protecting the sperm and allowing them to survive to fertilize an egg. 

Finally the bulbourethral glands, produce a lubricating fluid that cleans and neutralizes any remnants of urine in the urethra, facilitating smoother sperm passage. 

The final area is the urethra. Contractions of muscles around the prostate, seminal vesicles, and vas deferens push sperm and seminal fluid into the urethra and out of the body. (Ejaculation)

Summarized Pathway:

1. Testes ( production of sperm ) 

2. Epididymis ( maturation and storage ) 

3. Vas Deferens ( transport ) 

4. Seminal Vesicles, Prostate Gland, Bulbourethral Glands (addition of fluids)

5. Urethra ( final passage and ejaculation ) 

Describe the important  hormonal controls that regulate the male reproductive system

The important hormonal controls are 

1. Gonadotropin Releasing Hormone ( GnRH ) 

• Produced by the Hypothalamus

• Function: Released in pulses to stimulate the anterior pituitary gland to release two important gonadotropins: Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH). 

2. Luteinizing Hormone (LH)

• Produced by: Anterior Pituitary

• Function: LH stimulates the Leydig cells in the testes to produce testosterone. Testosterone is the primary male sex hormone responsible for the development of male secondary sexual characteristics, and the maintenance of sperm production. 

3. Follicle-Stimulating Hormone (FSH) 

• Produced by Anterior pituitary

• FSH works in conjunction with testosterone to stimulate the Sertoli cells in the seminiferous tubules of the testes. These cells nourish and support the developing sperm, aiding in spermatogenesis ( the production of sperm ). 

4. Testosterone

• Produced by: Leydig cells in the testes

• Function: Testosterone is crucial for the development of male reproductive tissues, such as the testes and prostate. It also promotes the secondary sexual characteristics of males and regulates sperm production in the testes. Testosterone exerts negative feedback on both the hypothalamus and pituitary gland to regulate the levels of GnRH, LH and FSH. 

5. Inhibin

• Produced by Sertoli cells in testes

• Function: Inhibin is involved in a negative feedback mechanism that regulates FSH secretion from the anterior pituitary. When sperm production is sufficient, inhibin is released to inhibit further secretion of FSH, ensuring that spermatogenesis does not exceed the necessary rate. 

6. Estrogen

• Produced by Sertoli cells and adrenal glands 

• Function: While traditionally thought of as a female hormone, estrogen is also present in males. It is involved in the regulation of spermatogenesis and has other psychological roles, though its precise function in males is still under study. 

7. Prolactin

• Produced by: Anterior pituitary

• Function: Primarily responsible and associated with milk production and females. Male function of this hormone is unclear. 

 Hormonal Regulation Feedback Loops:

Negative feedback: Both testosterone and inhibin exert negative feedback on the hypothalamus and pituitary gland to regulate the production of GnRH, LH, and FSH, maintaining balance in the system. High levels of testosterone reduce GnRH and LH secretion, while inhibin reduces FSH secretion when sperm production is adequate. 

Positive Feedback: At certain times (example: puberty), GnRH can stimulate an increase in LH FSH production, leading to an increase in testosterone production. 

Describe the important hormonal controls that regulate the female ovarian cycle.

1. Gonadotropin- Releasing Hormone (GnRH)

• Produced by Hypothalamus

• Function: Stimulates the anterior pituitary to release FSH and LH. 

• Cycle timing: Released in a pulsatile fashion, with frequency and amplitude changing across the cycle. 

2. Follicle - Stimulating Hormone (FSH)

• Produced by: Anterior pituitary

• Function: Stimulates growth and maturation of ovarian follicles (which contain the eggs)

• Cycle Phase: Predominantly active during the follicular phase (first half of the cycle). 

3. Luteinizing Hormone (LH)

• Produced by: Anterior pituitary

• Function: Trigger ovulation (the release of the mature egg from the dominant follicle). 

• Stimulates formation of the corpus luteum from the remnants of the follicle. 

• Cycle phase: Sharp LH surge around the middle of the cycle causes ovulation.

4. Estrogen (mainly estradiol) 

• Produced by: Growing ovarian follicles (granulosa cells) 

• Functions: Promotes development of the uterine lining ( endometrium )

• Moderate levels, inhibits FSH and LH (negative feedback) 

• At high, sustained levels ( just before ovulation ), triggers positive feedback to stimulate the LH surge. 

• Cycle phase: Rises during the follicular phase and peaks just before ovulation. 

5. Progesterone

• Produced by: Corpus luteum (after ovulation) 

• Functions: Maintains and further develops the endometrial lining for implantation. 

• Inhibits GnRH, LH, and FSH (negative feedback) to prevent additional ovulations during the cycle. 

• Cycle Phase: Dominant during the luteal phase (second half of the cycle) 

6. Inhibin 

• Produced by: Granulosa cells of the follicle and corpus luteum. 

• Function: Inhibits FSH production to regulate follicle development

• Cycle phase: Present throughout but especially in the late follicular and luteal phases. 

   Phase Key Hormones Events

Halfway up

PAstels

Describe the important hormonal controls that regulate the female uterine cycle.

The female uterine cycle is known as the mestrual cycle. 

1. Menstrual Phase ( Days 1-5 ) 

• Trigger: Drop in estrogen and progesterone as the corpus luteum degenerates ( if no pregnancy occurs) 

• Effect: The endometrial lining sheds, resulting in menstruation. 

• Hormonal Status:

- Low estrogen & progesterone

- Rising FSH begins to stimulate follicle growth for the next cycle

2. Proliferative Phase (Days 6-14) 

• Trigger: Rising estrogen levels from developing follicles

• Effect: Stimulates regeneration and thickening of the endometrium. Endometrial glands and blood vessels grow in preparation for implantation. 

• Hormonal status:

- High Estrogen

- Low progesterone

- Ends with the LH surge that triggers ovulation

3. Secretory Phase ( Days 15-28)

• Trigger: After ovulation, the corpus luteum forms and secretes progesterone (and some estrogen) 

• Effect: Progesterone makes the endometrium thicker, more glandular, and vascularized, secreting nutrients for a potential embryo. 

If Fertilization Occurs:

• The embryo releases hCG (human chorionic gonadotropin), which maintains the corpus luteum. 

• Progesterone and estrogen remain high, preventing menstruation and supporting pregnancy. 

Phase Main Hormone            Endometrial Change