Lesson 77 Mammary glands structure and function

Mammary glands

4-5 pairs or 8-12 mammary glands starting from thoracic to inguinal region

Cats mammary glands

around 10. only 1 pair in inguinal region

mammary glands nerve supply

sympathethic→ spincter and blood vessel

sensory of skin→ ventral cutaneous branches of thoracic spinal and lateral cutaneous of lumbar spinal nerves

Lympahtics of mammary gland

drainage via axillary or superficial inguinal lymph nodes

mammary glands in cows

4 teats or 2 pairs. one mammary gland per teat (mamma)/ one lactiferous sinus

base of udder merge with body wall

separated in middle(left and right) by median intermammary groove, has fore and hind quarters

what does the 500:1 milk ratio in dairy cows imply about milk production

extremely high blood circulation is require to sustain high milk yield

what type of cell actively synthesizes milk within th eaveoli of lactating mammary gland

epithelial cells

Lactiferous sinus

milk storage compartment + site for cannulation or teat dilators

composed gland sinus and teat sinus

teat canal/ papillary duct has longitudinal folds projecting into the sinus

blood suppy to mammary glands

caudal superficial epigastric vein anastomose with cranial superficial epigastric vein. together they for “milk vein” or subq abdominal vein

why should the milk vein/ subcutaneous abdominal vein not be used from venipuncture

thrombophlebitis/ blood clots

nerves of mammary gland

T13, L1, L2, L3 supply skin of teats, base and cranial parts of udder

-aka costoabdominal, iliohypogastric, ilioinguinal and genitofemoral

Genitofemoral nerve passes through inguinial canal to ___

parenchyma of udder and teat

How do you anesthetize teat for surgery

ring block around base of the teat

mammary gland function

alveoli

functional unit of mammary gland/ udder

epithelial cells

lines cavity of alveoli and synthesizes milk

myoepithelial cells

surround the secretory epithelial cells in alveoli and help it squeeze to let milk down

alveoli is richly vascularized because it needs nutrients and water for milk. how much is produced in a day?

60L/day which needs 30,000 L of blood circulation through the mammary gland a ratio of 500:1 (blood to milk)

milk composition

proteins, carbs, lipids, minerals ,vitamins, and bioactive substance like immunoglobulins and antimicrobials

what is a determinant factor for milk synthesis

glucose

fat synthesis in each species

non-ruminant: glucose dependent

ruminants: acetate

proteins in milk is synthesized where

epithelial cells

how is lactose synthesized

glucose and galactose→ GLUTs→ into epithelial cell to golgi apparatus→ lactos synthesized→ lactose vesicles released into alveolar lumen

How is the milk composed of mostly water

lactose and salt act as osmotic regulators and draw water from blood into alveolar lumen

phases of milk production

induction phase: onset of milk production

maintenance phase: enhancement of established lactation

lactogenesis/induction phase

milk procution triggered by hormonal changed at parturition

-withdrawal progessterone→ cortisol increases and induce prolactin receptors→ increase prolactin few days before birth

-epithelial cells differentiate into active secretory cells

galactopoeiesis

sustains milk secretion after initiated, suckling/ milking stimulates this phase

-somatotropin change liver, fat, and muscle metabolism to favor milk synthesis

liver: gluconeogenesis

adipocytes: lipolysis

muscle: inhibit glucose utilization

-cortisol: protein synthesis, increased glucose uptake in the glands

-oxytocin: milk let down

prolactin

stimulate alveolar growth and milk production, and milk protein genes

continious milk secretion depends on regular milk removal what are the two reflexes

prolactin reflex for lactogensis

oxytocin reflex for milk let down

prolactin reflex

VIP-vasoactive intestinal peptide stimulate release of prolactin

dopamine-inhibits prolactin→ no lactation

oxytocin reflex

suckling causes oxytocin release

-intra-alveolar pressure needs to be low for milk production to continue if pressure too high milk production stops