CTW: Appreciating Gender Differences: Physiology

• Size, weight and body shape:

• Men weigh more and are taller on an average. Women have a larger hip section than men,for giving birth to infants with large skulls
• Strength, power and muscle mass: 
• Females have less total muscle mass than males. Males are stronger than females.
• Skeleton: 
• Males have denser, stronger bones, tendons, and ligaments.Male and female pelvises are shaped differently. The female pelvis features a wider pelvic cavity, which is necessary when giving birth.
• The female pelvis is larger and broader than the male pelvis which is taller, narrower, and more compact. The female inlet is larger and oval in shape, while the male inlet is more heart-shaped.
• Respiratory System :
• Males typically have larger tracheae and branching bronchi, with about 56% greater lung volume per body mass.
• Skin and Hair: 
• Male skin is thicker (more collagen) and oilier (more sebum) than female skin,[29] but females have a thicker layer of fat under the skin. Males also generally have darker skin than females. The lighter skin in females helps their bodies synthesize more Vitamin D from sunlight and absorb more calcium, which is needed during pregnancy and lactation. Men have more body hair than females 
• Sensory systems
• Women are more sensitive to smell and have more pain receptors on their body.In addition to defined diseases and syndromes, many common “everyday” pains appear to overburden women rather than men. Therefore, studies consistently find that women report more severe pain, more frequent pain, longer-lasting pain, and wider-ranging pain than men.[94] For example, common painful conditions such as dysmenorrhea may predispose females to more widespread musculoskeletal pains.
• Brain and Nervous System:

• Human males, on average, have larger brains than females. According to a 1995 study, female brains are more compact than male brains in that, though smaller, they are more densely packed with neurons, particularly in the region responsible for language.
• Intelligence: In studies concerning intelligence, it has been suggested that the ratio of brain weight to body weight (rather than actual brain weight) is more predictive of IQ levels. While men's brains are an average of 10-15% larger and heavier than women's brains, some researchers propose that the ratio of brain to body size does not differ between the sexes.However, some argue that since brain-to-body-size ratios tend to decrease as body size increases, a sex difference in brain-weight ratios still exists between men and women of the same size.
• Auditory and Language Related Regions: 
• Studies using MRI scanning have shown that the auditory and language-related regions in the left hemisphere are proportionally expanded in females versus in males.
•  Conversely, the primary visual, and visuo-spatial association areas of the parietal lobes are proportionally larger in males.

Speech and Language: The corpus callous is located at the sagittal divide and is the primary commissure in the human brain. It connects the left

and right hemispheres of the cerebral cortex, which allows them to communicate with each other. With respect to language, males predominantly use their left hemisphere but females use both their right and left hemispheres. The right hemisphere controls emotion, so using the right hemisphere adds more prosody to speech.In males, the corpus callosum is larger than females.[71] However, the splenium and the isthmus subregions of the corpus callosum are larger in females. The genu subregion is larger in males. These subregions may serve as the basis for sex differences in language.

• Memory Storage and Spatial Mapping: 
• The hippocampus has been proven by imaging to be larger in women than men. The hippocampus is crucial for memory storage and spatial mapping of the physical environment. This structural difference may be responsible for variations in behavior between the sexes.
• Navigation: Studies show that women are more likely to navigate using landmarks, while men are more likely to estimate distance in space or orientation.
• Chronic Stress Studies of rats show that males could learn better in the face of acute stress, while chronic stress is dealt with better by females. Sex hormones may influence female hippocampal cells to tolerate brain damage better than the same cells in men. The studies of the rats' influx and deflation of hippocampal cells can be translated to the difference in memory and spatial behaviors between the sexes
• Amygdala:
• The amygdala, which is the structure that responds to emotionally arousing information, respond to the environment and reacts with stress. The male amygdala is proportionally larger than that in women, causing sex to be a determining factor in reactions to stress. In studies of rats, there are more numerous interconnections seen in males in regard to this structure, suggesting the same pattern in humans. Katharina Braun and company (Otto von Guericke University, Magdeburg, Germany) studied a litter of Degu puppies removed from their mother and determined that hearing their mother's call produced a higher concentration of serotonin in males' amygdala and a decreased concentration in females' amygdala. In this case, stress causes females' emotion regulation to drop, while males seem to keep more of an even keel. While this study was limited to rodents, it provides a possible explanation of why anxiety disorders occur more often among human females than males

References:
Psychology of women: A Handbook of Issues and Theories
The Psychology of Women- Helene Deutsch
Sex Differences in Human Psychology
Sex Differences in Human Physiology
Emotions during Menstrual Cycle- womenshealth.about.com
Emotions during Menstrual Cycle- Dr Christina Hebbert