Mammary Gland

Question 1

Lymphatics

Answer 1

Lymphatics
● The thoracic and cranial abdominal mammary complexes drain into the axillary
lymph node
● The caudal abdominal and inguinal mammary complexes drain into the superficial inguinal lymph node (also called mammary lymph node)

Question 2

Innervation

Answer 2

Innervation
● Mammary glands receive sensory, sympathetic and parasympathetic innervation

● Thoracic mammary glands are innervated by lateral and medial mammary branches
of the cutaneous part of the intercostal nerves
● The abdominal and inguinal mammary glands are innervated by the cutaneous
branches of the iliophypogastric, ilioinguinal and genitofemoral nerves

● Inguinal mammary glands receive additional innervation from the mammary branch of the distal cutaneous branch of the pudendal nerve and the genitofemoral nerve

● Hormones from the hypophysis and other endocrine organs influence the secretion of
the mammary glands as well

Question 3

Neuro hormonal reflex arc

Answer 3

Neuro hormonal reflex arc
● Definition: responsible for the initiating and maintaining lactation.

● Mammary glands stimulated by suckling —> sensory nerve fibres conduct the
impulses to the central nervous system —> impulses trigger production of OXYTOCIN
within the hypothalamus and its release through the neurohypophysis —>
oxytocin causes contraction of the myoepithelial cells in the walls of the duct system
in the mammary glands, and the milk is ‘let down’.

● The effect of oxytocin is antagonized by ADRENALINE, which is released under stress

Question 4

Number of mammary complexes

intersp.

Answer 4

● Carnivores: 10 (8-12) complexes with 5-20 units each

● Pig: 14 complexes with 2-3 units each

● Small ruminants: 2 complexes with 1 unit each

● Bovines: 4 complexes with 1 unit each

Question 5

Suspensory apparatus of the mammary glands

Answer 5

● Apparatus suspensorius mammarius

● Extends the mammary glands from the ventral aspect of the trunk by the superficial
and deep layers of the external fascia of the trunk

○ Lateral fascial sheet (lamina lateralis): composed largely of dense connective tissue

○ Medial fascial sheet (lamina medialis) : composed largely of elastic tissue

○ Thin lamellae extend from both

● The left and right row of mammary complexes are divided by the intermammary
groove (sulcus intermammarius)

Question 6

Structure

Answer 6

● Each mammary complex comprises one or more mammary units

● The mammary body consists of epithelial glandular tissue ( glandulae mammaria )
and interstitial connective tissue ( interstitium ) with nerves, blood and lymph vessels

● Mammary unit ends with a system of ducts (with species specific arrangement)

● The duct system of each mammary unit can be subdivided into:
○ Glandulae alveolus : place of milk production
○ Ductus lactiferi : system of ducts for the transport of milk
○ Sinus lactiferi : sinus for the bulk of the milk

● Glandular tissue is arranged in lobules
( lobuli glandulae mammariae ), which
comprise a multitude of alveoli
(actual sites of milk production and secretion)

Question 7

● Milk:

Answer 7

○ Drains into intralobular duct

○ That joins others to form a larger interlobular duct

○ Which leads to a system of lactiferous
ducts that ultimately convey the milk to
the large lactiferous sinus

○ 1 lactiferous duct = drains 1 mammary lobe
○ 1 intralobular duct = drains 1 lobule

Question 8

The lactiferous sinus

Answer 8

○ Gland ( pars glandularis sinus lactiferi )
○ Teat sinus ( pars papillaris sinus lactiferi )
○ Transition between the two is marked by a mucosal fold

Question 9

Mammary gland blood supply

Answer 9

Mammary glands blood supply

ARTERIES
● The thoracic and cranial abdominal mammary complexes receive blood from the
mammary branches of the cranial superficial epigastric artery

● Ventral intercostal branches of the internal thoracic artery may also contribute to
the thoracic glands

● The caudal abdominal and inguinal mammary complexes are supplied by mammary
branches of the caudal superficial epigastric artery (ex. A. Pudenda externa)

VEINS:
● Thoracic mammary complexes drain into the cranial superficial epigastric —>
cranial epigastric —> internal thoracic

● Abdominal and inguinal mammary complexes drain into caudal superficial
epigastric —> external pudenda