Avian Flashcards
Describe avian heart adaptations due to metabolic demands.
-high oxygen demands
-large stroke vol
-large cardiac output
Describe the avian cardiovascular anatomy.
-avian heart twice as big
>varies w species, habitat, natural history
-heart found in cranioventral part of coelomic cavity
>single cavity w no partition by a diaphragm
-heart apex surrounded by liver
Describe avian 4 chamber heart.
-thin walled RV sickle moon shape
-LV cone shaped & reach apex of heart
-between RA & RV = rectangular shaped muscular AV valve (unique to avian heart)
Describe the arteries & BP of avians.
- Arteries
-lower peripheral vascular resistance
-stiffer arteries due to increased collagen fibers
>high BP - BP
-arterial BP is a function of:
A) cardiac output (CO)
CO = HR x SV
B) arterial impedance (afterload)
-108-250mmhg avg rate
*high pressure = aortic rupture, heart failure, hemorrhage -> death in stressed avians
Describe avian erythrocytes.
-nucleated & elliptical in shape
-functional mitochondria (?role)
>may have role in immune function
-involved in toxin metabolism & detoxification functions
-respond to environmental hypoxia (ex. High alt flight)
>modulate erythrocyte conc of other nucleotide triphosphates to adjust Hb-O2 affinity to enhance O2 uptake/unloading
-avian spleen can’t store RBCs
>RBCs production & Hb synthesis regulated independently
Hematopoiesis pathway regulated
Describe the respiratory physiology of avians.
-adapted to meet O2 demands of flight
-sep respiration & gas exchange functions
Describe upper respiratory system.
- Nares (diff color = diff sex)
-cd to beak (except kiwi)
-featherless cere
-operculum acts as baffle
-sides sep in some species (passerines) - Choana
-slit like opening in hard palate (incomplete)
-internal nares open to nasal passage & conchae - Choanal papillae
-epi project into choana
-lost w infection, VitA deficiency - Infundibular cleft
-opens to Eustachian tubes - Glottis
-opens at base of tongue
-not covered by epiglottis - Trachea
-complete, signet shaped cartilage
-overlap for flexibility
-large diameter lumen
>decreased resistance
-increased length
>increased tracheal dead space vol
-variations - Syrinx
-vocal apparatus
-modified tracheal cartilages form 2 membranes
-located around tracheal bifurcation
Describe the lower respiratory system.
- Parabronchi
*expansions in walls = atria
>air & blood move in opp direction = countercurrent
>air capillaries
>gas exchange most effective & takes place in the interparabronchial arterioles
>avian version of alveoli
[parabronchial lumen is perpendicular to the flow of deoxy blood]
a) paleopulmonic
-main gas exchange bronchi
-long & parallel
-one air flow, cd to cr
B) neopulmonic
-short & anastomose
-bidirectional air flow
-not all species have both - Lungs
-fixed position
-minimal change w respiration
-dorsal & lat recumbency decrease lung vol - Air sacs
-cr group: cervical, clavicular, anterior thoracic
-cd group: cd thoracic & abdominal
Describe the gas exchange, blood gas barrier.
-thinner compared to mammals
-smaller diameter of air capillaries
-more air capillaries = greater gas exchange
-unidirectional airflow (paleopulmonic system)
-blood flow at 90 degrees
Describe cross current flow.
-parabronchi & blood vessels at 90 degree angle
-air in lungs exposed to diff vessels
-decreasing oxygen tension meet unsat hemoglobin
-allows more efficient absorption of oxygen without high levels of CO2 in blood
Describe the two breath cycle.
continuous air flow
1. First inhalation
-air thru trachea to cd air sac
2. First exhalation
-from cd air sac into lungs
3. Second inhalation
-thru lungs into cr air sacs
4. Second exhalation
-from cr air sacs out thru trachea
Describe the air sacs during inspiration.
-air sacs only significant vol compliant structure in body cavity = vol increases
-as pressure becomes neg in air sac compared to atmospheric pressure -> air flows from atmosphere into pulmonary system
-as a result of inspiratory calving during inspiration there is little/no flow in ventrobronchi that connect the parabronchi & intrapulmonary bronchus = inspired has cont cd thru intrapulmonary bronchus
-portion of gas crosses neopulmonic lung & cont into cd thoracic & ab air sac = equal portion goes to dorsobronchi & across paleopulmonic lung
Describe contraction of expiratory muscles.
-internal vol of thoracoabdominal cavity decreases = pressure within air sacs increases & gas flow out of cd thoracic & ab air sacs & passes across neopulmonic lungs to paleopulmonic lungs & out the ventrobronchi & trachea to environment
-gas flow from cr air sacs dont pass back thru parabronchi but goes to ventrobronchi -> trachea -> environment
-during expiration = little/no flow in intrapulmonary bronchus as result of expiratory valving
Describe the kidney divisions in avians.
- Cr
-cr to ext iliac a - Middle
-between ext iliac a & ischiatic a - Cd
-cd to ischiatic a
Describe the 2 types of nephrons in avian kidneys.
no defined cortex, medulla, renal pelvis
1. Reptilian
-nephrons are smaller & more numerous with short intermediate seg between pros & distal convoluted tubules w no loop of henle
-CD not permeable to water (no absorption)
2. Mammalian
-cortical proximal & convoluted tubules & loop w thin & thick seg descending into medullary cones
-avian glomerulus has similar structure to mammalian
-CD not permeable to water (no absorption)
*hypotonic urine
Describe the avian urine SG.
Between 1.005 - 1.020 bc decreased capacity for conc urine (lower SG) = hypotonic urine
-10-30% mammalian & reptilian 70-90%
Describe the renal portal system.
-cd. Mesenteric v
>blood from hindgut
-ischiatic v
-int vertebral venous sinus
>blood from vertebral column
-int iliac v
>blood from leg region
-ring of vasculature (aka renal portal system)
>cr & cd renal portal vein that branch off L & R ext iliac v & L & R common iliac veins
Describe the renal portal system blood flow.
- Common iliac v
-valve resp for diverting blood away from or to kidneys
-innervated by adrenergic & AcH receptors - Blood flow to kidneys
-parasympathetic stim via AcH
-valve closure = blood flow into parenchyma of kidney - Blood flow to cd vena cava (skips kidney)
-sym stim via NE & EPI
-valve open = blood flow directly into vena cava to ensure venous return to heart during flight
Describe bird droppings.
- Urine
- Urates
- Feces
Describe avian ureters.
-lined by mucus secreting pseudostratified epi
-facilitate excretion of urates in colloidal suspension
-starts at cr division of kidney
-courses cd
-branch to middle & cd renal lobes ending in urodeum
Describe Urates/Uric acid.
-uric acid is the main nitrogen waste product
-protein -> AA + uric acid
-urates are small molecules that are freely filtered by glomerulus
>transported to prox tubule by renal portal system = venous blood to peritubular capillary plexuses
Describe uric acid & dehydration.
-urates have the potential for crystal formation in prox tube or ureter
>occur when conc of urates secreted into lumen increases past its solubility limit
-dehydrated patient = risk of sludge/obstruction
>normal hydrate provides a GFR sufficient to reduce that risk
Describe avian urine & urates.
-stored in urodeum
-poss to move from urodeum by retroperistalsis into lg intestine or colon
>water reabsorption
>electrolyte homeostasis
>nitrogen recycling
>energy source creation
—albumin -> degraded to AA, dipeptides, tripeptides -> bacteria use to make SCFAs
-retroperistalsis controlled by tonicity of fluid within GIT
>200 or higher than that of plasma = retrograde peristalsis slowed/stops
Describe avian types of breeders.
- Continuous
-reproduce thru yr - Seasonal
-reproduce in a season - Indeterminate
-resp to removal/addition of eggs during laying period by laying extra eggs or curtailing laying - Determinate
-# of eggs in clutch determined at onset of laying & unchanged by removal or addition of eggs
*brood patch = M & F
