Crunches or sit ups are good methods to strengthen the abdominal muscles
You inhale when contracting muscles and exhale when finishing a rep.
The first line of defence (or outside defence system) includes physical and chemical barriers that are always ready and prepared to defend the body from infection. These include your skin, tears, mucus, cilia, stomach acid, urine flow, 'friendly' bacteria and white blood cells called neutrophils. Hope this helps.
Proprietary hospitals offer all kinds of health care at one point, from preventive to emergency to follow up care.