Week 10 Lesson 77- Structure and Physiology of the Mammary gland

What is the extent of mammary chains in the dog and cat?

From the thoracic to the inguinal region.

How many pairs of mammary glands are typically found in dogs and cats?

4 to 5 pairs, totaling 8 to 12 glands.

What is the most common total number of mammary glands (mammae) in these species?

10 glands.

How many abdominal pairs of mammary glands does a cat possess?

Only one abdominal pair.

Which nerve system supplies the mammary sphincters and blood vessels?

The sympathetic nerve supply.

Which nerves provide sensory supply to the mammary skin?

Ventral cutaneous branches of thoracic spinal and lateral cutaneous branches of lumbar spinal nerves.

Where does the lymphatic drainage of the canine/feline mammary glands go?

To the axillary and superficial inguinal lymph nodes.

Approximately how much does a cow's udder weigh?

Around 10 kg.

How many mammae (or quarters) are present in the cow?

4 mammae or 2 pairs.

How many mammary glands are present per mamma in the cow?

One mammary gland per mamma.

What is the specific milk storage compartment in the cow's udder?

The lactiferous sinus.

What structure separates the left and right halves of the bovine udder?

The median intermammary groove.

What are the two distinct parts of the lactiferous sinus?

The gland sinus (cistern) and the teat sinus (cistern).

Where is the gland sinus located relative to the teat sinus?

It is the dorsal part of the lactiferous sinus.

What structures in the teat canal project into the teat sinus?

Longitudinal folds at the internal entrance.

What is the technical name for the teat canal?

The papillary duct.

What is a common clinical use for the teat canal site?

Cannulation and application of teat dilators.

How are the mammary veins positioned relative to the arteries?

They are satellite to the arteries.

What is another name for the caudal superficial epigastric vein?

The cranial mammary vein.

What vein does the cranial mammary vein anastomose with cranially?

The cranial superficial epigastric vein.

What is the common name for the subcutaneous abdominal vein?

The "milk vein".

Why is the milk vein not recommended for venipuncture if the jugular fails?

Risk of thrombophlebitis or blood clots.

Which nerve is represented by L1 in the bovine mammary supply?

The iliohypogastric nerve.

Which nerve is represented by T13 in the bovine mammary supply?

The costoabdominal nerve.

Which nerve is represented by L2 in the bovine mammary supply?

The ilioinguinal nerve.

Which nerve is represented by L3-L4 in the bovine mammary supply?

The genitofemoral nerve.

Which nerve supplies the caudal/pudendal region of the udder?

The pudendal nerve.

What parts of the udder do the T13, L1, and L2 nerves supply?

The skin, teats, base, and cranial parts.

Through what structure does the genitofemoral nerve pass to reach the udder?

The inguinal canal.

To which internal parts of the udder does the genitofemoral nerve provide supply?

The parenchyma of the udder and the teat.

What anesthetic technique involves injecting local anesthetic around the teat base?

A ring block.

What are the functional units of a lactating mammary gland?

Alveoli.

Which cells line the cavity of the alveoli and synthesize milk?

Epithelial cells.

Which cells surround the secretory epithelial cells to eject milk?

Myoepithelial cells.

Approximately how many alveoli are found in a cow?

Billions.

How do nutrients and water enter the epithelial cells from capillaries?

Via diffusion.

How many liters of blood must circulate to produce 1 liter of milk?

500 liters.

To produce 60 liters of milk per day, how much blood must circulate?

30,000 liters.

When does a female start lactation relative to parturition?

Immediately after parturition.

What is the overall process of milk synthesis called?

Lactogenesis.

What are some components of milk besides water and lactose?

Proteins, carbohydrates, lipids, minerals, vitamins, and bioactive substances.

What percentage of milk is typically water?

Approximately 88%.

What is the determinant factor for milk synthesis in the mammary gland?

Glucose supply.

What are the two specific precursors for lactose synthesis?

Glucose and galactose.

Which glucose transporters (GLUTs) are expressed in the mammary gland?

GLUT1 and GLUT8.

What is the primary precursor for fat synthesis in non-ruminants?

Glucose.

What is the primary precursor for fat synthesis in ruminants?

Acetate.

Where are most milk proteins synthesized?

Within the epithelial cells.

Where are glucose and galactose absorbed in the epithelial cells?

At the basal membrane.

In which organelle is lactose synthesized?

The Golgi apparatus.

How is lactose released into the alveolar lumen?

Via secretory vesicles from the apical membrane.

Besides lactose, what is the other main osmotic regulator in milk?

Salt.

What determines the amount of water absorbed into the alveoli?

Lactose.

When is water drawn into the secretory vesicles?

Before they are released into the alveolar lumen.

What is one of the main determinants of the total volume of milk produced?

Lactose.

What are the two distinct phases of lactogenesis?

The induction phase and the maintenance phase.

What happens during the induction phase of lactogenesis?

The onset of milk secretion.

What happens during the maintenance phase of lactogenesis?

Maintenance or enhancement of established lactation.

What is the technical term for the maintenance phase?

Galactopoiesis.

Which hormone is responsible for developing the ability for milk production in the induction phase?

Prolactin.

What triggers the induction phase?

Hormonal changes at parturition.

What hormonal change involves the withdrawal of a specific hormone prior to birth?

Withdrawal of Progesterone.

Why is progesterone withdrawal important for lactation?

Progesterone inhibits cortisol receptors.

What is the role of the increase in cortisol just before birth?

To induce prolactin receptors.

When does the increase in prolactin typically occur across species?

A few days before birth.

What do epithelial cells differentiate into during the induction phase?

Active secretory cells.

What effect does prolactin have on alveolar growth?

It stimulates alveolar growth.

Which milk protein gene expression is stimulated by prolactin?

Alpha-lactalbumin.

What are the two most important galactopoietic hormones?

Somatotropin (Growth Hormone) and Prolactin.

Where does Somatotropin promote metabolic changes to favor milk synthesis?

Liver, adipose tissue, and muscle.

What metabolic process does Growth Hormone promote in the liver?

Gluconeogenesis.

What process does Growth Hormone promote in adipocytes to provide energy?

Lipolysis.

What does Growth Hormone inhibit in muscle to conserve nutrients?

Glucose utilization and amino acid oxidation.

Does Somatotropin have a proven direct effect on the udder?

No proven direct effect.

Which hormone is considered the primary lactogenic hormone?

Prolactin.

How is the galactogenic effect of prolactin described compared to its induction effect?

It is more subtle.

Which hormone has a synergistic effect with Prolactin for protein synthesis?

Glucocorticoids (Cortisol).

What effect do glucocorticoids have on glucose in the mammary gland?

They increase glucose uptake.

Where are glucocorticoid receptors specifically located?

In the glandular tissue.

What physical action is essential for the maintenance phase of lactation?

Milk removal by suckling or milking.

What are the two specific reflexes stimulated by regular milk removal?

The Prolactin reflex and the Oxytocin reflex.

What is the purpose of the Prolactin reflex?

For lactogenesis (milk synthesis).

What is the purpose of the Oxytocin reflex?

For milk let-down.

Which peptide stimulates the release of Prolactin?

Vasoactive Intestinal Peptide (VIP).

Which neurotransmitter inhibits the release of Prolactin?

Dopamine.

What effect do dopamine agonists have on lactation?

They inhibit lactation.

Where are the touch/heat receptors that initiate milk let-down located?

In the teats.

Through which structure does the sensory signal for let-down travel first?

The spinal cord.

Where is oxytocin released from following the sensory signal?

The posterior pituitary.

How does oxytocin reach the mammary gland from the pituitary?

Via blood circulation.

What cells contract in response to oxytocin?

Myoepithelial cells.

What happens to intra-alveolar pressure if milk is not removed?

It increases.

What is the result if intra-alveolar pressure remains high?

Milk production ceases.

What increases in the alveolar lumen when myoepithelial cells contract?

Hydrostatic pressure.

Into which structures is milk secreted when the alveoli contract?

Lobular ducts.

When does the mammary gland become functional during pregnancy?

During the second half of pregnancy.

Which hormone is the main one responsible for milk synthesis?

Prolactin.

Which hormone is responsible for milk let-down?

Oxytocin.

How are both prolactin and oxytocin released during lactation?

Through neuroendocrine reflexes.

What is the specific glucose transporter expressed at the apical membrane?

GLUT12.