Quiz 1 Flashcards

Question

Alveolar Structure

Answer 1

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

Answer 2

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

Answer 3

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

Answer 4

(Gland sinus) – Holds up to 400 milliliters of milk – Collecting area for the mammary ducts

Answer 5

(cricoid fold; cisternal ringfold) – separates gland and teat cisterns

Answer 6

(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)

Answer 7

(teat canal) – Functions to keep milk in udder and bacteria out of udder

Answer 8

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

Answer 9

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)

Answer 10

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)

Answer 11

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

Answer 12

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

Answer 13

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

Answer 14

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

Answer 15

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

Answer 16

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

Answer 17

Branch from mammary arteries Found in the teat

Answer 18

From internal iliac Only supplies upper rear portion of the gland

Answer 19

Below inguinal canal Allows for downward distension of udder when it fills with milk Relieves stress on external pudic artery

Answer 20

Essentially no crossover of arterial blood supply between udder halves

Answer 21

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

Answer 22

Left and Right Pudic (Pudendal) Veins Femoral Vein Iliac Veins Posterior Vena Cava Right Atrium of Heart

Answer 23

Cranial Mammary Veins Subcutaneous Abdominal Vein Xiphoid Cartilage (“milk wells”) Thoracic Veins Brachial Veins Jugular Veins Anterior Vena Cava Right Atrium of Heart

Answer 24

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

Answer 25

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!

Answer 26

Heart Rate and Stroke Volume

Answer 27

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