Why so many poses good for digestive?

http://www.yogajournal.com/poses/finder/anatomical_focus/digestive_organs

Yoga postures and treatment of symptoms of cross-table
Items	Autonomic nervous system disorders	Bad sleep	Neurasthenia	Endocrineproble	Anxiety	Constipation	Headache	sexualproblem	shoulder stiffness	Tinnitus
Plow			※		※	※	※	※	※	※
Twist							※	※	※
Cobra	※			※	※			※
head stand	※						※
shoulderstand		※	※				※		※
Fish		※	※
gate			※			※			※
handstand				※				※
sun salutation	※				※			※
wheel	※					※			※
forward bend				※					※
wide-angle			※
locust					※
Cat					※
Savasana					※
Bow	※
Tree	※
Camel										※
Hanumanasana				※				※
Triangle								※
abdominal massage						※
reclining big toe stretches						※
Pigeon						※
warrior								※

• By the from, we really can to clearly distinguish the effect of these actions in these way? 

I made another from to describe a few common effect of these position.

items	Effect	note
Snake	Fit curve(Chin, chest muscles  )、Strengthen the back muscles，Improve back muscles,  back pain relieve.
Wheel	Strengthen the back, wrist, ankle and thigh muscles or have more power. To relax shoulder and neck muscle. keeping the spine health and flexibility. strengthen abdominal muscles, increase gastrointestinal peristalsis. prevent constipation increase the memory.
Tree	strengthen the legs, back and chest muscles and the two ankles.  Hips relieve .  Breath and chest beneficial. Improve the stability of posture and balance.  Enhance the capacity of your mind and focus on.
Fish	Correct curved ischium, prevention of arthritis,neuralgia, rheumatism, gout generation. Also contributed to the kidney, liver physiology, enhancedbronchial, lymph, nasal allergy, treatment of diabetes.
Gate	Can strong leg, abdomen, back, to increase the power of these three, and enhance the nervous system,spleen, liver, gallbladder and other functions.
plow	strenth whole spine 、stimulate circulation.	Old and weak people should consult a doctor before .
Shoulder stand	Concentration of blood to the spine that in to tough and flexible. Reduce leg varicose veins. Strengthen the throat. Massage thyroid, promote the secretion of hormones to maintain the body's metabolism, and promote health. Prevention of stroke, visceral ptosis, constipation.	This pose need build -up experience by the yoga teacher 's watch.
Camel	Can stretch and strong spine. improve circulation . Expand the chest or strengthen the lungs to increased lung capacity. humpback and correct drooping shoulder and poor posture.