Topic 69 - Role of calcium and phosphorus, absorption, distribution and excretion

Question 1

Words to include in role of calcium and phosphorus

Answer 1

• Structural development of the body

Calcium

• Hemostasis
  
  • Ca²⁺, factor IV
    
    • Activates:
      
      • Factor II (Prothrombin)
      • Factor X (Stuart-Prower)
      • Factor XII (Thromboplastin Antecedens)
      • Factor XIII (Lóránd-Laki)
• Muscle contraction
  
  • Ca²⁺ → troponin c → cross-bridge cycle
• Excitability
  
  • George formula (emperical)
• Effects on cardiac muscles
  
  • Myoplasmatic calcium level in cardiac muscle
    
    • Muscle stretch ↑
  • SDD and contractility
    
    • Dependent on EC Ca²⁺ concentrations
• Capillary permability
  
  • ​CAM (Cell Adhesion Molecule)
    
    • Integrins
• Membrane stabilization
  
  • Glycocalyx
    
    • Ca²⁺ function as glue
• Enzyme activity
  
  • Lipease
  • Renin
• Shaping the form
  
  • Development of skeletal system
    
    • Hydroxyapatitie (Bone, together with phosphorous)
    • Calcium carbonate (Egg shell)
• Signal
  
  • Ca²⁺ released from IC stores → affecting cellular processes

Phosphorus

• Structural element
• Energy balance
• Regulatory processes
• Intermediary metabolism
  
  • ​Cellular metabolism
  • Phosphorylation (activation)
  • Dephosphorylation (inactivation)
  • Kinase
  • Phosphatse
• Storage of chemical energy
  
  • ​Macroergic phosphate
    
    • ATP
    • Creatine phosphate (CrP)
• Ridgity of bone
  
  • ​Hydroxyapatite (together with calcium)
• Nucleic acids
  
  • ​Storage and transmission of genetic information
• Buffer system
  
  • ​Phosphate buffer
  • Primary phosphate: H₂PO₄^-
  • Secondary phosphate: HPO₄^2-
• Membrane composition
  
  • ​Construction of hydrophilic components in biological membranes
    
    • Phospholipids

Question 2

Words to include in absorption of calcium and phosphorus

Answer 2

Regulation of absorption of Ca & P metabolism

• Absorption depends on actual needs of organism
  
  • Eg: Absorption ↑ → milk production ↑ → lactation → parathyroid hormone ↑, D-hormone ↑
• Foodstuff provides necessary Ca/P ratio
  
  • Juvenile animals: 1:3:1
  • Adult animals: 1:55:1
  • During egg-laying period 3:5:1
• Vitamin D supply
• Decreasing need of Ca and P with age
• Local intestinal factors
  
  • Increasing factors:
    
    • pH ↓
    • Protein level ↑
    • Lactose ↑
  • Decreasing factors
    
    • pH ↑
    • Fast intestinal peristalsis
    • Fe, Mg, F
    • Oxalic acid
    • Phytates

Question 3

Words to include in distribution of calcium and phosphorus

Answer 3

Calcium

• Distribution:
  
  • Bone: 80%
  • EC calcium fractions (EC, plasma): 20%
• Total calcium:
  
  • Mammals: 2.5 mmol/l
  • Birds: 5 mmol/l
• ISF: 1.7-1.8 mmol/l

Phosphorus

• Plasma phosphorus: 4 mmol/l
• Inorganic phosphate distribution:
  
  • Secondary phosphate (HPO₄^2-): 80%
  • Primary phosphate (H₂PO₄^-): 20%
• Saturated solution: Ca²⁺ x HPO₄^2-

Question 4

Words to include in excretion of calcium and phosphorus

Answer 4

Calcium

• Feces: 90%
  
  • Passing intestines: 1/3
  • Secreted with intestinal fluid: 2/3
• Urine: 10%
  
  • Regulated:
    
    • Parathryoid hormone (PTH) ↓
    • Calcitonin (CT) ↑
• Milk
  
  • 2 g/100 bwt/day

Phosphate

• Regulated excretion by kidney: 95%
  
  • Parathryoid hormone (PTH)
  • Calcitonin (CT)
  • D-hormone
• Milk
  
  • Lactating animals: 1g/100 kg bwt/day

Question 5

Give the role of calcium

Answer 5

• Essential in structural development and various regulatory mechanisms

1. Hemostasis
   
   • ​​Ca = factor IV, which activates:
     
     • Factor II (Prothrombin)
     • Factor X (Stuart-Prower)
     • Factor XI (Thromboplastin Antecedens)
     • Factor XIII (Lóránd-Laki)
   • Removal of calcium from serum provides the most common wat to inhibit blood coagulation
2. Muscle contraction
   
   • ​Calcium → troponin C → cross-bridge cycle​
3. Excitability
   
   • ​​George formula​
     
     • ​Excitability:
       
       • ​[Na⁺] x [K⁺] / [Ca²⁺] x [Mg²⁺] x [H⁺]
4. Effects on cardiac muscle
   
   • _​_Myoplasmatic calcium level in cardiac muscle increases with stretching the muscle
   • Excitability is proportional to EC calcium levels, while muscle is inversely proportional to it
5. Capillary permability
   
   • ​​Permeability of a capillary is dependent on the presence of calcium
6. Membrane stabilization
   
   • ​In construction of glycocalyx, calcium serves as “glue”
7. Enzyme activity
   
   • _​​_Lipease
   • Renin
8. Shaping the form
   
   • ​​Essential in development of skeletal systems:
     
     • ​Bone: hydroxyapatite
     • Egg shell: calcium carbonate
9. Signal
   
   1. ​Important role as IC signal

Question 6

Give the role of phosphrus

Answer 6

• Major structural element
• Involved in energy balance and regulatory processes

1. Intermediary metabolism
   
   • ​​Important in cellular metabolism
     
     • ​Phosphorylatin: activated
     • Deposphorlyation: inactivated
2. Storage of chemical energy
   
   • ​​Macroergic phosphate:
     
     • ​ATP
     • Creatine phosphate
   • Storage of feed-derived energy in chemical forms is connected with the presence of phosphorus
3. Ridgity of bone
   
   • ​​Hydroxyapatite (together with Ca²⁺)
4. Nucleic acids
   
   • _​​_Storage and transmission of genetic information requires phosphorous
5. Buffer system
   
   • _​​_Phosphate buffer
   • Primary phosphate (H₂PO₄^-)
     
     • In urine
     • Able to remove H⁺ in chemical bonds
   • Secondary phosphate (HPO₄^2-)
     
     • Plasma component
     • Its presence in glomerular filtrate allows binding of a high amount of tubular H⁺
6. Membrane composition
   
   • ​​Essential in construction of hydrophilic components in biological membranes:
     
     • ​Phospholipids

Question 7

Regulation of absorption in calcium and phosphorus

Answer 7

• Absorption mainly depends on needs
• Foodstuff provision necessary Ca/P ratio:
  
  • Juvenile animals: 1.3:1
  • Adult animal: 1.55:1
  • During egg-laying period: 3.5:1
    
    • Birds need an extremely high amount of calcium: egg-shell contains hardly any phosphorus
• Vitamin-D supply
  
  • ​Vitamin-D is a determining factor of calcium utilization
• Age
  
  • ​Need of calcium and phosphorus is decreasing with age
• Local intestinal factors
  
  • ​Increasing factors:
    
    • ​Low pH
    • High protein level
    • High lactose (suckling animal)
  • Decreasing factors:
    
    • ​High pH
    • Fast intestinal peristalsis
    • Fe, Mg, F
    • Oxalic acid
    • Phytates

Question 8

Distribution of calcium

Answer 8

• Distribution:
  
  • 80% bone
  • 20% EC calcium fractions (EC, plasma)
• Calcium fractions
  
  • Total calcium:
    
    • Mammals: 2.5 mmol/l
    • Birds: 5 mmol/l
  • ISF: 1.7-1.8 mmol/l

Question 9

Distribution of phosphorus

Answer 9

• Total plasma phosphorus: 4 mmol/l
  
  • ​Phospholipids
  • Inorganic phosphate
  • Phosphate esters
• Distribution of inorganic phosphate:
  
  • 80% secondary phosphate HPO₄^2-
  • 20% primary phosphate H₂PO₄^-
• Ca²⁺ x HPO₄^2-: saturated solution
• Plasma phosphorous concentration des not play a direct regulatory role

Question 10

Excretion of calcium

Answer 10

• In feces: 90%
  
  • 1/3 calcium passing by the intestines
  • 2/3 calcium secreted with intestinal fluid
• In urine: 10%
  
  • ​Regulated:
    
    • Parathyroid hormone (PTH) ↓
    • Calcitonin (CT) ↑
• In milk

Question 11

Excretion of phosphorus

Answer 11

• Regulated excretion by kidney: 95 %
  
  • Parathyroid hormone (PTH)
  • Calcitonin (CT)
  • D-hormone
• Milk (lactating animals)