Understanding Human Anatomy and Physiology

Posted on Feb 10, 2025 in Biology

Factors Influencing Follicle Count in Women

Q: What factors modify the number of follicles a woman has?

A: Women are born with approximately 1 million follicles. During the aging process, they lose follicles, and by puberty, they have around 300,000 to 500,000 follicles. By the age of 40, women have only 3% of their original follicle count. Smoking, stress, poor diet, and lack of exercise can decrease the quantity and quality of follicles.

Perineum Structure

Q: What structures make up the Perineum?

A: The perineum is a diamond-shaped space between the pubic symphysis (anteriorly), the coccyx (posteriorly), and the ischial tuberosities (laterally). It lies just inferior to the pelvic diaphragm (levator ani and coccygeus). It is divided transversely into two triangles:

  • Anterior Urogenital Triangle: Includes the external genitalia.
  • Posterior Anal Triangle: Contains the anus.

The perineum is also divided into superficial and deep layers, with some muscles common to both men and women.

Muscles of the Urogenital and Anal Triangles

Q: What muscles make up the Urogenital and Anal (Pelvic) triangles/diaphragms?

A:

  • Urogenital Diaphragm (Superficial and Medium Plane):
    • Sphincters: Internal and external urethra and anus
    • Bulbocavernosus (Bulbospongiosus)
    • Ischiocavernosus
    • Deep and superficial transverse perineal muscles
  • Pelvic Diaphragm (Deep Plane):
    • Anus elevators:
    • Puborectalis
    • Pubococcygeus
    • Iliococcygeus
    • Levator ani

Muscles in the inferior view:

  • Pubis
  • Urethra
  • Sacrum
  • Coccyx
  • Sciatic tuber
  • Anterior/Urogenital Triangle
  • Posterior/Anal Triangle
  • Vagina
  • Vestibule
  • Anus
  • Bulbospongiosus muscle
  • Ischiocavernosus muscle
  • Superficial transverse perineal muscle
  • External Anal Sphincter
  • External urethral sphincter
  • Levator ani
  • Puborectalis

Urinary System Function

Q: What is the function of the Urinary System?

A: The primary function is cleansing the blood and ridding the body of wastes. However, it also plays crucial roles in:

  • Regulation of pH (shared with the lungs and blood).
  • Regulation of blood pressure (shared with the heart and blood vessels).

Micturition Center and Nerve Control

Q: Where is the micturition center in the spinal cord? Which nerves control voluntary and involuntary micturition?

A: The micturition center is located in the sacral segment of the spinal cord, between S2 and S4. The nerves involved are:

  • Hypogastric (involuntary)
  • Pelvic (involuntary)
  • Pudendal (voluntary)

Urinary Infections in Women

Q: Why do women have more urinary infections than men?

A: Women are more susceptible to urinary infections due to the short length of the female urethra (approximately 4 cm). This provides a smaller barrier to fecal bacteria compared to the longer male urethra.

Micturition Reflex

Q: How does the Micturition Reflex happen?

A: The micturition reflex is triggered by stretch receptors in the bladder wall. These receptors transmit nerve impulses to the sacral region of the spinal cord, generating a spinal reflex. This results in:

  • Parasympathetic neural outflow causing contraction of the detrusor muscle.
  • Relaxation of the involuntary internal urethral sphincter.
  • Inhibition of somatic motor neurons, leading to relaxation of the skeletal muscle of the external urethral sphincter.

Mechanical Digestion

Q: During the digestive process, what happens in mechanical digestion?

A: Mechanical digestion reduces the size of food particles to increase both surface area and mobility. This includes:

  • Mastication (chewing) and tongue movements.
  • Churning of food in the stomach, further breaking it down and exposing more surface area to digestive juices, creating chyme.

Functions of Pharynx and Esophagus

Q: What are the functions of the Pharynx and Esophagus?

A:

  • Pharynx: Propels food from the oral cavity to the esophagus.
  • Esophagus: Propels food to the stomach.

Importance of the Mouth in Digestion

Q: What is the importance of the mouth in the digestive process?

A: The mouth plays several crucial roles:

  • Ingests food.
  • Chews and mixes food.
  • Begins the chemical breakdown of carbohydrates.
  • Moves food into the pharynx.
  • Begins the breakdown of lipids via lingual lipase.