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
Describe male anatomy of avians.
-testes w coelomic cavity
-dimensions of testis increase w sexual activity
>seasonal birds & some passerines = testicular mass increase up to 500x
>increased length & diameter of seminiferous tubules & increase # of interstitial cells in resp to LH & FSH
-ductus deferens enter dorsal wall of urodeum
Describe the female anatomy of avians.
-Functional L ovary & oviduct
-R side of repro tract only develops in beginning of embryonic phase & remains vestigial
Describe the ovary & oviduct.
- Ovary
-follicle hierarchy
-after ovulation fails = no functional CL
-persistent cells secrete hormones during regression = lead to cystic follicles - Oviduct (5 portions):
>infundibulum
>magnum
>isthmus
>uterus
>vagina
Describe how an egg is made.
- Ovary goes to infundibulum
-captures ovulated ovum
-site of fertilization
-L ab air sac surrounds ovary (conduit)
-sperm penetration occur before albumen is laid down
-thin layer of albumen
>chaliziferous layer surrounds yolk after secreted
*CLIN APP: egg yolk peritonitis/egg related coelomitis - Magnum
-majority of albumen added - Isthmus
-formation of 2 shell membranes
>inner & outer shell
-makes sulfur containing AA - Uterus or shell gland spends most time here
-cr portion:
>adds water & electrolytes to albumen
-distal portion:
>creates shell via extraction of Ca from bloodstream - Vagina
-conduit for egg to pass from oviduct to cloaca
-fossulae spermaticae = sperm storage - Oviposition
-physical process of laying eggs
Describe a fully formed egg.
- Germinal disc
-ovum fertilized = blastoderm -> becomes embryo - Yolk
-lipoproteins & phosphoproteins
-main source of nutrition for embryo - Yolk membrane
-4 membranes
-barrier between yolk & albumen
-allows movement of electrolytes - Albumen
-suspends embryo in aqueous environment
-protein component nutrition source
-antibacterial properties
-dense albumen = chalaziferous layer
-thin albumen - Chalaza
-twisted strand of ovomucin fibers
-keeps yolk center in egg - Shell
-two shell membranes - Testa (inner)
>calcite = crystalline form of calcium carbonate - Cuticle (outer)
>water repellent, reduce evaporation loss, barrier for microorganisms
-air cell at blunt end = made as egg cools after laid
Describe Ca metabolism for eggshells.
egg = 10-20% of total body Ca
2 sources of Ca = bone & dietary Ca
-depends on available dietary Ca
>if diet has low Ca then medullary bone makes more Ca to compensate
>bone contributes more at night or lower Ca diet
-high labile reservoir found in medullary bone = enough Ca for 1 egg
>dietary Ca = replenish medullary bone reservoir
Describe what Ca homeostasis is regulated by.
-PTH
-Calcitonin
-Vit D (calcitriol)
-sex hormones
-response in mins
Describe PTH VS Calcitonin.
- PTH
-made by parathyroid gland
-chief cells (oxyphil absent)
-promote Ca absorption from bone (high blood Ca)
-induce rapid change in Ca osteoclast activity & Ca transfer by osteoblasts & osteocytes - Calcitonin (decrease blood Ca)
-made by ultimobranchial glands
-2 cell types that both make calcitonin
A) Principle cells
B) Morphologically distinct endocrine cell type
birds cant be hypocalcemic
Describe calcitriol.
-vit D
-increases absorption of Ca across duodenum & jejunum
-PTH resp for Ca mobilization from medullary bone
-imp for translocation of Ca across oviductal wall
>calbindin proteins in distal portion of uterus (oviduct) = levels rise during egg laying
>controlled by sex hormones not calcitriol
Describe estrogen.
-affect Ca metabolism
-increased Ca storage, mobilization, transportation
-increased estrogen causes osteoblasts to make medullary bone
>labile source of Ca when dietary supply is insufficient
>complete mineralization occur if calcitriol levels enough
>occur in long bones
-decreased estrogen cause osteoblast to make lamellar cortical bone & medullary bone goes away
