Question

1. What is the functional relationship between the integumentary and skeletal systems?
2. How does failure to maintain homeostasis in the integumentary system affect bone formation and remodeling processes? Be sure to discuss how the different types of bone cells respond to different factors (e.g., ions, hormones, cellular signaling molecules, etc.) and what the driving force behind maintaining homeostasis in the bone remodeling process.
3. Describe the pathogenesis of osteoporosis and explain why it is considered a multifactorial disease.
4. How do current therapies address these failures to maintain homeostasis and ameliorate the effects of osteoporosis?

Answer 1

Ans ;

1.  The skeletal system is the series of bones that provide structural support for the body. The integumentary system is the skin, hair, nails, and exocrine glands in the skin that provide the body with a protective barrier against the external world.

The skeletal system is absolutely dependent on the integumentary system (the skin) for the calcium that keeps the bones hard and strong. The relationship is indirect: In the presence of sunlight, a vitamin D precursor is produced in the dermal capillary blood. It is activated elsewhere, and (among its other roles) it regulates the carrier system that absorbs calcium from ingested foods into the blood. Because calcium is required for so many body functions, and bones provide the “calcium bank,” the bones become increasingly soft and weak in the absence of vitamin D because no daily rations of calcium are allowed to enter the blood from the digestive tract

2.

The epidermal layer of human skin synthesizes vitamin D when exposed to UV radiation. In the presence of sunlight, a form of vitamin D3 called cholecalciferol is synthesized from a derivative of the steroid cholesterol in the skin. The liver converts cholecalciferol to calcidiol, which is then converted to calcitriol (the active chemical form of the vitamin) in the kidneys. Vitamin D is essential for normal absorption of calcium and phosphorous, which are required for healthy bones. The absence of sun exposure can lead to a lack of vitamin D in the body, leading to a condition called rickets, a painful condition in children where the bones are misshapen due to a lack of calcium, causing bowleggedness. Elderly individuals who suffer from vitamin D deficiency can develop a condition called osteomalacia, a softening of the bones. In present day society, vitamin D is added as a supplement to many foods, including milk and orange juice, compensating for the need for sun exposure.

In addition to its essential role in bone health, vitamin D is essential for general immunity against bacterial, viral, and fungal infections. Recent studies are also finding a link between insufficient vitamin D and cancer

3. Osteoporosis :

Osteoporosis is a multifactorial disorder associated with low bone mass and enhanced skeletal fragility. Although most prevalent in older females, some men are also at high risk. Risk factors in men and women include smoking, family history of fracture, age greater than 65 years, and low but also high BMI particularly in men. Secondary causes of osteoporosis include chronic treatment with glucocorticoids, gastrointestinal disorders, diabetes mellitus (T1D, T2D), rheumatoid arthritis, liver disease, gluten enteropathy, multiple myeloma and other hematologic disorders. However, primary osteoporosis is most often related to either postmenopausal estrogen loss or age-related deterioration of skeletal microarchitecture; both are due to uncoupling in the bone remodeling unit. Reduced bone formation with age is almost certainly a function of impaired stem cell differentiation into the osteoblast lineage with a resultant increase in marrow adipogenesis. Increased bone resorption also characterizes most forms of osteoporosis but the etiology is multifactorial. Changes in local and systemic growth factors are often responsible for uncoupling between resorption and formation. However, alterations in peak bone acquisition contribute years later to low bone mass and enhanced skeletal fragility. Fracture risk assessment tools (e.g. FRAX) in handheld apps and computers which combine bone density score and risk factors, have provided rapid assessments of future osteoporotic fractures and can be performed at the bedside. Newer methods of measuring bone quality have led to insights into micro-architectural deterioration that contributes to skeletal fragility. Notwithstanding, low areal bone mineral density by DEXA remains the strongest predictor of subsequent fracture beyond age, and this is potentially measurable in everyone after age 65