Quiz 1 Flashcards
Phsiology
“A branch of biology that deals with the functions
and activities of life or of living matter (as organs,
tissues, or cells) and of the physical and chemical
phenomena involved”
Lactation
To secrete milk
What is a Mammal?
The word mammal comes from the Latin mamma, meaning breast
* All mammals (monotremes, marsupials, placentals):
– Have hair
– Have mammary glands (nutrient transfer in form of milk)
– Are warm-blooded
– Are vertebrates
– Use lungs to breathe air
– Give birth to live young (*monotremes don’t!)
What are the three classes of mammals
Monotremes (Prototheria)
Marsupials (Metetheria)
and
Placentals (Eutharian) - Diverged about 80 Million Years Ago
What is the composition of milk like for each class of mammals
Monotremes and Marsupials - Milk composition changes considerably throughout lactation: Early milk is very simple and it becomes more nutrient dense as lactation progresses and the young requires more nutrients
Placentals - Milk is consistent and complex throughout the entire lactation
Mammary Gland
any of the large compound modified sebaceous glands that in female mammals are modified to secrete milk, are situated ventrally in pairs, and usually terminate in a nipple”
What system is the mammary gland part of?
The Reproductive System -
The mammary gland is loosely considered part of the reproductive system:
– Serves a “reproductive function”; nourishment of the neonate = survival of species.
– Relies on same endocrine (hormonal) support for development and function.
Example: gonadal steroids, prolactin, etc
What is the role of the Mammary Gland
Exocrine gland; common to all mammals
* Function: nourish the neonate
– Food source: fat, protein, sugar (CHO), vitamins, minerals, water
– Protection: immunoglobulins (first Ab protection; absorbed via intestinal tract)
Structure of mammary glands across species
Take any two mammals, mammary glands can vary in:
– Location
– Total number
– Openings per gland
In what regions can mammary glands be found
Thoracic
Abdominal
Inguinal
Describe Monotremes
Lay eggs (oviparous)
No placenta
Give birth to very immature young
“Pouchless”
Mammary hairs; no true nipples for the glands
Mammary hairs located diffusely
Mammary Gland:
Different appearances/ similar anatomy & function:
– Most primitive – Duck-billed Platypus
* simple tubules lined with secreting epithelial cells
* located within a pouch; no teats, milk is secreted onto hair
Describe Marsupials
Give birth to live young (viviparous)
Very rudimentary or no placenta
Give birth to very immature young
Have pouches
Mammary glands have nipples
Mammary Gland
Different appearances/ similar anatomy & function:
– Kangaroo & Opossum
* more complex, branching ducts; terminate in teats with many galactophores
Decribe Placentals
95% of mammal species
Give birth to live young
Placenta
Offspring born immature (not as much as monotremes and marsupials though)
No pouches
Mammary glands have nipples
The Mammary Gland (Farm Animals and Primates)
Highly developed branching ducts which terminate in Alveoli lined by epithelial cells
Location of mammary gland varies:
* Thorax - primates
* Inguinal - cattle, sheep, horses, goats
* Combination - dogs, hogs, rodents
What type of cells form the mammary gland
Skin Cells
Invagination of fetal ectoderm
Ectoderm (epithelial) cells form the glandular (parenchymal) component of the gland
Mesoderm forms the connective tissue support system (stroma)
Mammary Development During Fetal Life
Early Teat Formation - 55 days
Primary Sprout - 80 days
Secondary Sprouts - 90 days
Canalization of Primary Sprout - 100 days
Development of Gland and Teat Cisterns - 110-130 days
Development of Median Suspensory Ligament - 180 days
Mammary Gland and the Abdominal Cavity
The mammary gland is independent of the abdominal cavity except for necessary supply and drainage systems
What is the connection between the Mammary Gland and the Abdominal Cavity?
Inguinal Canal:
* blood vessels; arterial feed and venous drainage
* lymph vessels; lymph drainage
* nervous system; afferent (sensory) & efferent (autonomic (sympathetic/parasympathetic))
How much can the udder weigh?
Up to 165 pounds
What structures support the Mammamry Gland?
– Skin (minor role)
– Median (medial) suspensory ligaments
– Lateral suspensory ligaments
Median Suspensory Ligament
Separates right and left halves of udder
Main structural support
Is made of elastic tissue which responds to weight of milk in
udder
Lateral Suspensory Ligaments
Inflexible
Surround the outer wall of udder
Attached to prepubic and subpubic tendons
Secondary support
- Fore- and rear-udder attachments
Stroma
Support system / connective tissue
Parenchyma
Glandular, Secreting Tissue
-Alveoli
-Duct System
- Lobules and Lobes
What percentage of the mammary system is the rear quarters?
60%
Alveolar Structure
Alveolar components & function:
– epithelial cells - milk synthesis & secretion
– lumen - collect milk components & water
– myoepithelial cells - milk ejection
– basement membrane - selective transfer
– terminal duct - milk transport out of alveoli
– capillary system - supply milk precursors and deliver hormones
Alveolus
basic secretory unit; lined by epithelial cells which synthesize and/or secrete:
* lipid - fatty acids & triglycerides
* protein – enzymes & caseins
* lactose – disaccharide
– osmoregulatory molecule (draws water)
* minerals & vitamins - Ca, P, K; Vitamins A, B, C, D
* water – paracellular pathway
Mammary Ducts
Tubes from which milk drains from the alveoli to the
gland cistern
– Interlobar: primary ducts that drain multiple lobes
* Lined with two layers of non-secretory cells
* Many myoepithelial cells
– Intralobar: ducts within a lobe and drain several regions
of the lobe
– Interlobular: secondary ducts that drain multiple lobules
* Lined with 1 layer secretory cells
* Surrounded by myoepithelial cells
– Intralobular: small ducts within a lobule
– Intercalary/tertiary ducts: small ducts which exit the
alveolus
Gland Cistern
(Gland sinus)
– Holds up to 400 milliliters of milk
– Collecting area for the mammary ducts
Annular Ring
(cricoid fold; cisternal ringfold)
– separates gland and teat cisterns
Teat Cistern
(teat sinus)
– Duct in teat with capacity of 30-45 milliliters
– Separated from streak canal by folds of tissue called Furstenberg’s rosettes
- Cavity within the teat
– continuous with gland cistern
– lined with longitudinal and circular folds forming pockets
– fills with milk during milk letdown (30-40 mL)
Streak Canal
(teat canal)
– Functions to keep milk in udder and bacteria out of udder
Furstenburg’s Rosette:
mucosal folds of streak canal lining internal end of the canal
– can fold over canal opening when udder is full; major point
of entry for leukocytes leaving teat lining
What factors influence milk Synthesis?
Milk synthesis is dependent on:
– Number of secretingcells
– blood supply
– supply of milk precursor
– endocrine support for lactogenesis
– milking frequency
Number of secreting cells is dependent on:
– genetics
– endocrine support for mammogenesis
– nutrition
– disease (mastitis)
Blood Components
Blood Plasma
-60 % of blood volume
-Blood fluid minus cells
–Plasma components:
*Water = 90%
*Solids
Blood cells
–40% of blood volume
–≈7 million RBC per mL
–≈9000 WBC per mL
–WBC types
*Lymphocytes
*Leukocytes
*Polymorphonuclear neutrophils (PMNs)
Plasma Solids
Proteins:
- Albumins, carriers for steroid hormones
- Globulins, antibodies
– Hormones, steroids & proteins
– Clotting factors, fibrin, fibrinogen
–Amino acids
Salts; Ca, Cl , K, Na
Glucose
Minerals & vitamins
Short chain fatty acid;
–Acetate (C2)
– Propionate (C3)
–Butyrate (C4)
Glycerol, triglycerides
Function of Blood
Transport nutrients
–digestive tract (absorptive stage)
–storage (deliver to adipose, muscle, bone, liver tissue, etc.)
–mobilization (post absorptive stage)
Transport waste from tissues to renal system
Hormone transport from endocrine gland to target tissue
Maintain water balance
Mammary Blood Flow and Milk Yield
Mammary blood flow and MY are positively correlated
Blood flow through the capillary beds surrounding alveoli is essential to milk production
Regulated by microcirculation (flow of blood from arteriole to venule)
Local and systemic regulators of blood flow within the gland
–Oxygen, carbon dioxide, adenosine, lactic acids, pH
–PTHrP , serotonin, nitric oxide, IGF I
What is the importance of the Mammary Vasculature?
Critical for mammary function
All milk precursors come from the blood
400 500 units of blood pass through udder for each unit of milk synthesized (~280 mL/sec)
Total udder blood volume in a lactating cow is 8% of total body blood volume vs. 7.4% in a non lactating cow
2 - 6 fold increase in blood flow in the mammary gland 2 - 3 d pre partum
What are the main routes for Mammary Blood Flow?
Blood enters the udder through external pudic arteries
Blood exits udder from veins at the base of udder; two major routes
–Via external pudic veins
–Via subcutaneous abdominal veins
Arterial System Organization
Heart
Abdominal aorta
Internal/external iliacs
–Perineal artery from internal iliac supplies small portion of upper rear udder
Femoral
External Pudic pudendal
–Passes through inguinal canal
–Each one supplies one half udder
–Where blood enters the udder
Inguinal Canal
–Orifice in body cavity in inguinal region where blood vessels, lymph vessels and nerves enter and leave body cavity to supply skin in posterior part of animal
Mammary artery (1cm diameter)
– Cranial: supplies front side of udder
– Caudal: supplies rear side of udder
Papillary Arteries
Branch from mammary arteries
Found in the teat
Perineal Artery
From internal iliac
Only supplies upper rear portion of the gland
Sigmoid Flexure
Below inguinal canal
Allows for downward distension of udder when it fills with
milk
Relieves stress on external pudic artery
No Anastomoes
Essentially no crossover of arterial blood supply between udder halves
Venous System
Mammary veins leave udder antiparallel to arteries
3 veins on each side carry blood from udder
–External pudic vein (2 3 cm diameter)
*Empties into iliacs and then posterior vena cava
*Contains sigmoid flexure
–Subcutaneous abdominal vein (MILK VEIN; 1 2.5 cm diameter)
*Enters at xiphoid process via milk wells
*Empties into anterior vena cava
–Perineal vein (0.5 cm diameter)
*Parallels perineal artery
*Carries <10% of blood leaving udder
Venous Circle
–Formed between anterior and posterior mammary veins
–Prevents pinching off of venous outflow when cow lies down
Major Venous Blood Flow from the Venous Plexus
Left and Right Pudic (Pudendal) Veins
Femoral Vein
Iliac Veins
Posterior Vena Cava
Right Atrium of Heart
Minor Venous Blood Flow from the Subcutaneous Abdominal Vein
Cranial Mammary Veins
Subcutaneous Abdominal Vein
Xiphoid Cartilage (“milk wells”)
Thoracic Veins
Brachial Veins
Jugular Veins
Anterior Vena Cava
Right Atrium of Heart
Alveolar Diffusion Pressure
Capillary pressure in the udder ≈ 25 mmHg
–this represents the diffusion pressure of solutes into the mammary cell from blood
*As alveolar pressure increases, diffusion of solutes from blood into the mammary epithelial cells slows
Important factors affecting intramammary pressure and diffusion gradient:
Oxytocin release (posterior pituitary) may increase intra alveolar pressure to > 60 mmHg
Failure to remove milk (> 14 hrs.) will retard diffusion (and milk synthesis) if pressure within the alveolus > 25 mmHg
Both these conditions will reduce or inhibit milk synthesis!
What is Blood Flow a function of?
Heart Rate and Stroke Volume
Calculating Cattle Blood Flow
Cattle heart beat rate ≈ 60 - 80/min
Stroke volume ≈ 0.9 liters (636 kg/1400 lb cow)
Blood volume ≈ 8 % BW (8 lbs./gal.)
What volume of blood would a 636 kg Holstein pump per day?
*636 kg Cow, 0.9 liters/heart stroke
*Volume/day = 0.9 L x 70 strokes/min = 63 liters/min
*63 liters/min x 1440 min/day =90,720 L / day =24,000 gal/day
How many total blood volume changes does this amount to?
Volume changes per day:
*636 kg Cow x 8% = 51 L blood = 13.5 gallons
*Volume changes/day = 90,720 L / 51 L = 1,780 volume changes/day
