MCB 135E: Discussion

Discussion Topics

• Lactation

• Gastrointestinal System

• Liver

Lactation

• Mammary Gland Development

• Milk Production, Ejection, Cessation

• Benefits of Breast Feeding

Mammary Gland Development

• 6th week of gestation– Formation of mammary ridges

• Further development under influence of E (pre-natal)

• Female breasts develop further at puberty– Again primarily under influence of E

– Enlargement due to fat deposits and connective tissue

– Further growth and branching of ductal system

Mammary Gland: Pregnancy

• Higher levels of E lead to more ductal elongation• Influenced also by GH, PRL, Insulin, and

glucocorticoids• Final development of gland due to influence of P

– Causes branching and formation of alveoli buds at ends of ducts

– Alveoli are lined with milk secreting epithelium

Benefits of Breast Feeding

• Infant– Reduction in infections

– Initial increased growth

– Decreased obesity in adulthood

– Positive effects on mental development

• Mother– More rapid and

sustained weight loss

– Lactational amenorrhea

• Decreased Breast Cancer ?

– Psychological benefits

G.I. System

• GI Functions– Digestion and Absorption– Defense– Endocrine– Mechanical and Chemical

• Nutrition of the Infant

G.I. System Development

• Smaller size = Shorter duration of food in GI• Developing Stomach

– Spitting, Regurgitating, burping are a result of peristalic waves in opposite direction

– Emptying time • First Month – 1-4 Hours

• Adult – 5-6 Hours

– Size (Volume) much smaller at birth with continual increase in size until adulthood

Nutrition

• Proteins– Synthesized in alveolar cells– Casein and lactalbumin are

predominant proteins– Have antigenic properties

• Vitamins– No supplements required for

infant while breast feeding

• Minerals– Mother needs to take

calcium supplements

• Fats (Breast Milk)– High in essential FA

required for brain and retina development

– Secreted in droplets pinched off from cell into alveolus

• CHO– Lactose

– Glucose

– Galactose

Liver• Functions

– Formation of Bile– CHO storage– Formation of Urea– Cholesterol Metabolism– Make plasma proteins– Regulates fat metabolism– Metabolizes some polypeptide hormones– Reduction and conjugation of steroid hormones– Vitamin D3 metabolism– Detoxification

Bile

• Functions– Emulsification of lipids– Activation of enzymes for

digestion of lipids– Conjugation of bilirubin to

form a water soluble product for excretion

– Excretion of cholesterol– Excretion of drugs, heavy

metals, and environmental toxins

– Neutralization of acid delivered to duodenum from stomach

• Constituents– Water (97%)– Bile Salts– Bile Pigments

(Bilirubin and Biliverdin)

– Cholesterol– Inorganic Salts– Fatty Acids– Lecithin