B. Half of the total genetic information
Stem cells arise from the inner mass of the cell
Signalling factors trigger differentiation in stem cells
Genes that lead to the production of undifferentiated blood cells are activated
Signalling factors cause undifferentiated blood cells to produce red blood cells
Explanation:
Red blood cells are formed in the bone marrow. The precursor to the RBC is stem cell which is undifferentiated and pluripotent. The stem cell gets differentiated to form immature RBCs. Immature RBC then gets divided and becomes mature. Stem cell giving rise to RBC is called Haemoctytoblast. The process of erythropoiesis takes 2 days to form new red blood cells
Answer:
Following are the roles of the digestive, excretory and endocrine systems in terms of homeostasis:
- The endocrine system regulates the secretion of various hormones and homeostatic mechanisms in response to signals of the hypothalamus and pituitary glands.
- The excretory system maintains homeostasis by purifying the blood and getting rid of toxic waste from the blood.
- The digestive system is mainly involved in the transfer and regulation of nutrients from food.
Explanation:
Role of Endocrine System:
- The endocrine system mediates all the chemical signaling in the body.
- Hormones are chemical messengers that the endocrine system uses to maintain chemical homeostasis.
- Endocrine system manages glucoregulation by controlling the secretion of the hormones glucagon and insulin by the pancreas. Low and high blood sugar levels are sensed by the brain which then signals the endocrine system to release glucagon and insulin respectively.
- The endocrine system is also indirectly involved in thermoregulation. A low core temperature signal received by the hypothalamus initiates the release of TSH by the pituitary gland and then that of T3, T4 thyroid hormones that stimulate shivering thermogenesis in the skeletal muscles.
Role of Digestive System:
- The digestive system regulates the amount of nutrients absorbed in the body.
- Although the absorption of nutrients in food is not exactly according to bodily needs, the absorption of dietary iron and calcium is strictly regulated by the digestive system.
Role of Excretory System:
- The excretory system carries out osmoregulation which is the maintenance and regulation of water and salt levels in the blood.
- The excretory system regulates the excretion of toxic waste from the blood.
- Excess water, salts, urea and bilirubin (produced as a result of RBC break down) are some of the excretions.
That would be double. The polar ends go inside, so they face each other, leaving the non-polar sides to face on both the inside and outside linings of the cell.
