Part 1 Flashcards
Cardio-respiratory physiology- Avian
what are 3 heart adaptions to to extreme metabolic demands?
High Oxygen demands
larger stroke volumes
larger cardiac outputs
Cardio-respiratory physiology- Avian
How big is the avian heart?
What factors affect this (3)?
Mass of avian hearts typically twice the size of the mammals hearts.
Varies based upon:
species, habitat
natural history
Cardio-respiratory physiology- Avian
Where specifically is the heart found?
Heart found within the cranioventral part of the coelomic cavity
Cardio-respiratory physiology- Avian
what is the coelomic cavity?
Coelomic cavity is a single cavity with no further
partitioning by a diaphragm
Cardio-respiratory physiology- Avian
What surrounds the heart apex?
liver
Cardio-respiratory physiology- Avian
How many chambers does the heart have?
what are they, where are they located in relation to each other?
4-chamber heart
* Thin-walled right ventricle which is a sickle-moon shape
around the thick-walled left ventricle
* Left ventricle is cone-shaped and extends to apex of heart
* Atrioventricular opening on left side is a tricuspid valve
* Between right atrium and ventricle is a rectangular-shaped
muscular atrioventricular valve unique to avian heart.
* Believed to support complete emptying of right
ventricle
Cardio-respiratory physiology- Avian
Arteries: what is peripheral vascular resistance
The resistance in the circulatory system that is used to create blood pressure, the flow of blood and is also a component of cardiac function.
Cardio-respiratory physiology- Avian
Arteries: is peripheral vascular resistance higher or lower?
lower
Cardio-respiratory physiology- Avian
Are arteries “stiffer” ?what does this mean?
“Stiffer” arteries (increased collagen fibers)
* Means higher blood pressure is required
Cardio-respiratory physiology- Avian
Blood Pressure:
Arterial blood pressure is a function of what?
- Arterial blood pressure is a function of
- 1) Cardiac Output (CO)
- CO = heartrate x stroke volume
- 2) Arterial impedance (afterload)
Cardio-respiratory physiology- Avian
what is the average range of blood pressure?
why is this clinically important?
- 108-250 mm Hg (average range)
- Clinical importance?
- Consequences of this high pressure can however mean that aortic rupture, heart failure and hemorrhage are
a common cause of death in stressed avian patients.
Cardio-respiratory physiology- Avian
What are Avian Erythrocytes? what shape are they?
- Red Blood Cells (RBCs)
- Nucleated and elliptical in shape
Cardio-respiratory physiology- Avian
Avian Erythrocytes
do they have functional mitochondria? why/why not?
yes
- Functional mitochondria
- Exact role unclear and if they function similar to other somatic cells
- Hypothesis: serve as providers of electron donors, reservoir of
antioxidants, and a system for maintaining ion homeostasis - Hypothesis: contribute to thermogenesis
- Hypothesis: Provide better control of the Hb-O2 binding affinity (due
to flight demands)
Cardio-respiratory physiology- Avian
Avian Erythrocytes
what about nucleus and ribosomes? why/why not?
- Still unclear whether nucleus and ribosomes are fully functional in avian
erythrocytes - May have role in immune function
- Phagocytosis, antigen presentation, interleukin-like production occur
Cardio-respiratory physiology- Avian
Avian Erythrocytes
Are they involved in toxin metabolism and/or detoxification functions?
Why?
- Involved in toxin metabolism and detoxification functions
- Thought to be due to the endoplasmic reticulum and associated enzymes
*
Cardio-respiratory physiology- Avian
Avian Erythrocytes
what is environmental hypoxia?
How are red blood cells involved?
- Suggested to respond to environmental hypoxia (e.g. high altitude flight)
- Modulating erythrocyte concentrations of other nucleotide triphosphates (i.e. ATP produced by
the mitochondria) to adjust and fine tune Hb-O2 affinity to enhance O2 uptake and/or unloading.
Cardio-respiratory physiology- Avian
Avian Erythrocytes
can the avian spleen store erythocytes?
- Avian spleen are not capable of storing erythrocytes
Cardio-respiratory physiology- Avian
Avian Erythrocytes
How does Erthrocyte production and Hb synthese differ in birds? Why?
- Erythrocyte production and Hb synthesis are regulated independently in birds, whereas these are coupled in
mammals - Hematopoiesis pathway is regulated in avian erythrocytes
Cardio-respiratory physiology- Avian
what is the adaptation used to meet oxygen demands in flight?
Separates respiration and
gas exchange functions
Cardio-respiratory physiology- Avian
Adaptations to meet oxygen
demands of flight
Mammalian v. Avian
Trachea and bronchi
1-Width?
2-length?
3-dead space?
Mammalian v. Avian
larynx v. syrinx
1-width: narrower v wider
2-length: shorter v. longer
3-dead space: bigger v. smaller
Cardio-respiratory physiology- Avian
Adaptations to meet oxygen
demands of flight
Mammalian v. Avian
ventilation
1-gas flow?
2-mode of pulmonary flow?
3-stratification of inhaled gas?
4-separation of ventilation and gas exchange functions?
Mammalian v. Avian
Larynx v. syrinx
1-reciprocating v. unidirectional
2-convection AND diffusion v. diffusion
3-yes v. no
4-no v. yes
Avian have thinner BG barrier and rigid parenchyma compared to mammal
Na
Cardio-respiratory physiology- Avian
Adaptations to meet oxygen
demands of flight
Mammalian v. Avian
gas exchange/cross current gas exchange
Mammalian v. Avian
Larynx v. syrinx
no v. yes
Cardio-respiratory physiology- Avian
Upper respiratory system
nares- 4 features?
- Upper respiratory system
- Nares
- Located caudal to beak (except kiwi)
- Featherless cere
- Operculum acts as baffle
- Sides separate in some species (passerines)
Cardio-respiratory physiology- Avian
Upper respiratory system comprised of 5 things:
1-incomplete hard plate
2. choana
3. choanal papillae
4. infundibular cleft
5. Glottis
Cardio-respiratory physiology- Avian
Upper respiratory system
what is the Choana?
Choana * Slit-like opening in hard
palate
* Internal nares, opens to
nasal passages and
conchae
Cardio-respiratory physiology- Avian
Upper respiratory system
what is the choanal papillae?
Choanal papillae * Epithelial projects into
choana
* Lost with infection, Vit A
deficiency
Cardio-respiratory physiology- Avian
Upper respiratory system
what is the infundibular cleft?
Infundibular cleft * Opens to eustachian tubes
Cardio-respiratory physiology- Avian
Upper respiratory system
what is the Glottis
Glottis opens at the base of tongue
-not covered by epiglottis
Cardio-respiratory physiology- Avian
Upper respiratory system
Trachia 5 features?
clinical significance?
- Upper respiratory system
- Trachea
- Complete, signet-shaped cartilage
- Slight overlap for flexibility
- Larger diameter lumen
- Decreased resistance
- Increased length
- Increased tracheal dead space volume
- Variations
- Clinical significance?
Cardio-respiratory physiology- Avian
Upper respiratory system
syrinx 3 features?
- Syrinx
- Vocal apparatus
- Modified tracheal cartilages form 2 membranes
- Located around tracheal bifurcation
** see slide for more info.
Cardio-respiratory physiology- Avian
lower respiratory system
Parabronchi 2 parts?
do all species have both?
Paleopulmonic
neopulmonic
no
Cardio-respiratory physiology- Avian
lower respiratory system
Parabronchi Paleppulmonic definition?
- Paleopulmonic.
- Main gas exchanging bronchi
- Long and lie parallel to each other
- One-way air flow, caudal to cranial
**see slide for more info
Cardio-respiratory physiology- Avian
lower respiratory system
Parabronchi neopulmonic definition?
- Neopulmonic
- Short and anastomose profusely
- Bidirectional air flow
**see slide for more info
Cardio-respiratory physiology- Avian
lower respiratory system
Lungs
describe
clinical significance?
- Lower respiratory system
- Lungs
- Fixed position
- Minimal change with respiration
- Clinical significance: Dorsal and lateral recumbency may decrease lung volume
Cardio-respiratory physiology- Avian
lower respiratory system
Air Sacs
How many?
paired or single?
2 types, what are they called?
- Air sacs (typically 9, 8 paired, 1 single)
cranial
caudal
Cardio-respiratory physiology- Avian
lower respiratory system
Air Sacs
what are cranial?
- Air sacs (typically 9, 8 paired, 1 single)
- Cranial group: cervical, clavicular, anterior thoracic
Cardio-respiratory physiology- Avian
lower respiratory system
Air Sac
what are caudal
- Caudal group: caudal thoracic and abdominal
**see slides for detailed info
Cardio-respiratory physiology- Avian
- Gas exchange, blood-gas barrier
how are they the same/different than mammals?
how does the air flow?
how does the blood flow?
- Similar in structure to mammals, but thinner
- Smaller diameter of air capillaries
- More air capillaries in given space = greater gas exchange
- Unidirectional air flow in most lungs (paleopulmonic system)
- Blood flow is at 90 degrees
Cardio-respiratory physiology- Avian
3 features of Cross-current flow?
- Cross-current flow
- Parabronchi and blood vessels at 90-degree angle
- Air in lungs continuously being exposed to different (fresh) vessels
- Decreasing oxygen tension meets unsaturated hemoglobin
Cardio-respiratory physiology- Avian
explain two breath cycle?
- Two breath cycle
- First inhalation
- Air through trachea to caudal air sacs
- First exhalation
- From caudal air sacs into lungs
- Second inhalation
- Through lungs into cranial air sacs
- Second exhalation
- From cranial air sacs out through trachea
- Animation of air sacs and breathing:
- https://youtu.be/kWMmyVu1ueY
Cardio-respiratory physiology- Avian
explain two breath cycle? with detail.
Since the air sacs are the only significant volume-compliant
structures within the body cavity, their volume also increases.
As pressure within the air sacs becomes negative relative to
ambient atmospheric pressure, air flows from the atmosphere
into the pulmonary system. As a result of inspiratory valving
(see below), during inspiration there is no or little flow in the
ventrobronchi that connect the parabronchi and the
intrapulmonary bronchus and, as a result, the inspired gas
continues caudally through the intrapulmonary bronchus. A
portion of the gas crosses the neopulmonic lung and continues
into the caudal thoracic and abdominal air sacs, while an equal
portion goes to the dorsobronchi and thence across the
paleopulmonic lung (Fig. 3a and Fig. 3b).
During contraction of the expiratory muscles the internal
volume of the thoracoabdominal cavity decreases, pressure
within the air sacs increases, and gas flows out of the caudal
thoracic and abdominal air sacs, passes across the
neopulmonic lungs to the paleopulmonic lungs and thence out
the ventrobronchi and trachea to the environment (Fig. 3a and
Fig. 3b). Gas flow from the cranial air sacs does not pass back
through the parabronchi but goes to the ventrobronchi, the
trachea and thence to the environment. During expiration
there is little or no flow in the intrapulmonary bronchus as a
result of expiratory valving (see above).
why is the avian raspiratory system unique?
implication to gas exchange?
how does this impact the total gas exchange surface area?
how does this differ from mamals?
what is special about birds and a diaphram?
The avian respiratory system is unique as birds have small lungs, that have little change in volume when breathing, and air sacs, which act as bellows but do not
participate in gas exchange. This segregation of ventilation and gas exchange helps to increase the total gas exchange surface area. The bellows system allows
continuous gas flow as opposed to ‘in and out’ tidal flow of mammals. Birds have no diaphragm–instead the horizontal septum separates the lungs from the
viscera. This septum plays no active role in respiration but passively helps to displace the viscera during breathing.
B/c birds fly at high altitudes, what is the oxygen demand? lung efficiency? what 4 things are modified?
Flight and the ability to fly at altitude means that birds have much higher oxygen demands than mammals. Avian lungs are 10 times more efficient than
mammalian lungs in capturing oxygen due to the following modifications:
thin blood gas barrier
cross-current blood flow
one way air flow
rigid lung
what is the modification of the thin blood-gas barrier?
Thin blood-gas barrier: the air capillaries of the lung (equivalent to the mammalian alveoli) are finer and more numerous and the blood gas barrier is very thin.
This is possible because, unlike mammalian lungs which have to expand and contract with every breath, the fixed avian lungs require little interstitial tissue for
added strength.
what is the modification of the cross-current blood flow?
Cross-current blood flow: the blood flow is at right angles to air flow giving a cross current exchange system. This means that blood flow is always at right angles
no matter which way the air is flowing. Cross current exchange allows more efficient absorption of oxygen without incurring high levels of carbon dioxide in the
blood.
what is the modification of the one way air flow?
One way air flow: the air flow through the lungs is unidirectional as opposed to ‘in and out tidal flow’ of mammals. The parabronchi being tubes and not dead
end sacs like alveoli allows for continuous gas exchange in the avian lung and it may explain why birds can fly at high altitudes.
what is the modification of the rigid lung?
Rigid lung: the fact that the lungs are rigid and play no role in ventilation means that there is 20% more area for gas exchange than in mammals.
How many divisions of the avian kidneys? what are they?
- Kidneys divided into three divisions * Cranial * Cranial to the external iliac artery * Middle * Between the external iliac artery and the ischiatic artery * Caudal * Caudal to the ischiatic artery
what are the anatomical differences in avian kidneys?
- Avian kidneys
- No defined cortex, medulla, or renal pelvis.
- 2 types of nephrons
- Avian glomerulus has a similar structure and
function to its mammalian counterpart. - Hypotonic urine produced at this point
what are the 2 types of nephrons in Avian kidneys?
(no not black/white spotted and striped… those are cats lol)
2 types of nephrons
* Reptilian type
* Nephrons are smaller and more
numerous, with only a short, poorly
defined intermediate segment
between the proximal and distal
convoluted tubules with no loop of
Henle.
* Mammalian type
* Mammalian type has cortical proximal
and convoluted tubules and a loop
with thin and thick segments
what is the clinical significance of the anatomical differences in Avian kidneys?
- Avian urine specific gravity is typically between 1.005
and 1.020 g/mL because of birds’ decreased capacity
for concentrating urine - WHY?
**see slide here for more information
where does the renal portal system receive blood from? (4)
- Renal portal system receive blood from
- Caudal mesenteric vein
- Blood from hindgut
- Ischiatic vein
- Internal vertebral venous sinus
- Blood from vertebral column
- Internal iliac vein
- Blood from leg region
The ring of vasculature is also know as… 2 types, what are they?
- Ring of vasculature (aka renal portal system)
- Cranial and caudal renal portal veins that branch off the left and
right external iliac veins and left and right common iliac veins.
**see slide for more info
Renal Portal
System Blood
Flow
* Common iliac vein, what is it what does it do?
- Common iliac vein
- Valve responsible for diverting
blood away from or to the kidneys. - Innervated by adrenergic and
acetylcholine recepters
Renal Portal
System Blood
Flow
describe blood flow to kidneys?
- Blood flow to kidneys
- Parasympathetic stimulation via
acetylcholine - Valve closure = blood flow into the
parenchyma of the kidney.
Renal Portal
System Blood
Flow
describe Blood flow to caudal vena cava (skips
kidney)
Blood flow to caudal vena cava (skips
kidney)
* Sympathetic stimulation via
norepinephrine and epinerphrine
* Valve open = Blood flow directly into
vena cava to ensure venous return
to heart during flight
Bird droppings: Urine + Urates + Feces
- Bird droppings three components
- Bird droppings three components
- Urine
- Urates
- Feces
Bird droppings: Urine + Urates + Feces
- Avian ureter
what is it?
where is it?
what does it do?
- Avian ureter
- Lined by mucus-secreting pseudostratified epithelium
- Facilitates the excretion of urates in colloidal suspension
- Starts at the cranial division of the kidney
- Courses caudally
- Branches to the middle and caudal renal lobes ending in the urodeum
Urates = Uric Acid
- What are urates or uric acid?
- Uric acid is the main nitrogen waste product
- Protein amino acids + uric acid (“big picture”)
Urates = Uric Acid
* Are urates filtered by the kidney?
- Small molecule that can freely filtered by glomerulus
Urates = Uric Acid
* Are urates secreted by the kidney?
- Proximal tubule
- Primarily transported here by
- Renal portal system venous blood to the peritubular
capillary plexuses
Uric Acid and Dehydration
do the urates have teh potential for crystal formation?
if so when? where?
- Urates have the potential for crystal formation in proximal tube or
ureter - Occurs when concentration of urates secreted into the lumen
increases past its solubility limit
Uric Acid and Dehydration
- Clinical critical thinking question:
- What might be a concern related to a dehydrated patient,
urates, and GFR?
- Risk of sludge or obstruction
- Normal patient hydration provides a
GFR sufficient to reduce the risk of possible sludge formation or
obstruction
This is a common finding in free-ranging
birds found in a dehydrated and debilitated state.
Bird droppings: Feces + Urates + Urine
* Avian urine and urates
where are they stored?
- Stored in urodeum
Bird droppings: Feces + Urates + Urine
* Avian urine and urates
what is the process by which urodeum moves?
where does it go?
what are the 4 manners this can occur?
Possible to move from the urodeum by retroperistalsis into the large intestine or colon (+/-
cecum)
* Water reabsorption
* Electrolyte homeostasis
* Nitrogen recycling
* Energy source creation
Bird droppings: Feces + Urates + Urine
* Avian urine and urates
during the move from the urodeum by retroperistalsis describe the process of energy source reaction
- Energy source creation
- Albumin degraded to amino acids, dipeptides, tripeptides bacteria use to
produce SCFAs
Bird droppings: Feces + Urates + Urine
* Avian urine and urates
describe retroperistalsis
- Retroperistalsis controlled by tonicity of fluid within the GI tract
- 200 mOsm/kg or higher than that of plasma, retrograde peristalsis is significantly slowed or
stops
Avian Reproductive
Physiology
what are the 4 types of breeders?
continuous
seasonal
inderterminate
determinate
Avian Reproductive
Physiology
what is a continuous breeder?
- Types of breeders:
- Continuous
- Reproduce throughout the year
Avian Reproductive
Physiology
what is a seasonal breeder?
- Seasonal
- Reproduce in a particular season
Avian Reproductive
Physiology
what is an indeterminate breeder?
- Indeterminate
- Respond to removal or addition of eggs during the
laying period by laying extra eggs or curtailing laying
Avian Reproductive
Physiology
what is a determinate breeder?
- Determinate
- Number of eggs in clutch determined at onset of
laying and unchanged by removal or addition of eggs
Avian Reproductive
Physiology
what is a brood patch?
- Brood patch
- Females and males
Male Anatomy/Reproductive Physiology
what?
where?
what happens?
- Testes within coelomic cavity
- Dimensions of testis increase with sexual activity
- In seasonal birds and especially in some passerines, testicular mass can increase 300 to 500 times
- Increased length and diameter of the seminiferous tubules and to a greater number of interstitial cells, in response
to LH and FSH - Ductus deferens enters dorsal wall of urodeum
Female
Reproductive
Anatomy/Physiology
What?
where?
what unique aspect of ovary? why?
- Most birds have functioning left ovary and oviduct
- Right side of the reproductive tract only develops in the beginning of the embryonic
phase and remains vestigial - Unknown why unilateral development occurs
- One hypothesis: Reduction of body weight to improve the ability to fly
Ovary
&
Oviduct
3 facts about ovaries:
- Ovary
- Follicle hierarchy
- After ovulation fails no functional
corpus luteum - Persistent cells may secrete
hormones during regression;
however, can lead to cystic follicles
Ovary
&
Oviduct
How many portions of an oviduct and what are they called?
- Oviduct can be divided in five portions:
- Infundibulum
- Magnum
- Isthmus
- Uterus
- Vagina
How an egg is made
describe and explain Infundibulum:
where?
what does it do?
why?
when?
clinical relevance?
- Infundibulum
- Proximal opening in oviduct
- Responsible for capture of ovulated ovum
- Left abdominal air sac surrounds ovary except caudally
- Acts as conduit for ovulated ovum to “fall”
into opening of the infundibulum - Site of fertilization
- Sperm penetration must occur before the albumen
is laid down - ~15 minute window (chickens)
- Thin layer of dense albumen
- Chaliziferous layer, immediately surrounds yolk
after secreted - Clinical Relevance:
- Egg yolk peritonitis or egg-related coelomitis
How an egg is made
- Magnum
what
where
what occurs here?
- Magnum
- Location where majority of albumen is added
- Ovum remains here for ~2-3 hours
How an egg is made
- Isthmus
What happens here?
formation of what 2 things?
describe?
what ONLY happens here?
- Isthmus
- Formation of the two shell membranes
- Inner shell
- Outer shell
- Only location to produce sulfur-containing amino acids
- Important for shell membrane production
- Ovum remains here for ~1-2 hours
How an egg is made
- Uterus or Shell gland
what are theTwo anatomically distinct portions called, what do they do?
- Uterus or Shell gland
- Two anatomically distinct portions
- Cranial portion
- Responsible for adding water and electrolytes to albumen
- “plumping of the egg”
- Distal portion
- Pouchlike—site where egg remains for ~20 hours
- Creation of shell
- Extraction of calcium from bloodstream for formation
of shell
How an egg is made
- Vagina
what happens here?
- Conduit for egg to pass from oviduct to cloaca
- Fossulae spermaticae
- Special spermatic crypts for sperm storage up to several weeks
How an egg is made
- Oviposition
what is this?
- Oviposition
- physical process of laying eggs in birds
Fully formed
Egg
what are the 5 components?
- Egg components
- Germinal disc
- Yolk
- Yolk membranes
- Albumen
- Shell
Fully formed Egg
- Germinal disc
what happens here
what is the relevance of the “blastoderm”?
- Germinal disc
- If ovum is fertilized it is termed the blastoderm
- Will become embryo
Fully formed Egg
- Yolk
what is it made of?
what is its purpose?
- Lipoproteins and phosphoproteins
- Main source of nutrition for developing embryo
Fully formed Egg
- Yolk membranes
How many?
what do they do?
why?
- Yolk membranes
- 4 membranes
- Form a barrier between yolk and albumen
- Allows movement of electrolytes
Fully formed Egg
what is Albumen
what does it do
what is it made of, why
what special property does it have
2 kinds, what are they called?
- Albumen
- Suspends embryo in relatively aqueous
environment - Protein component nutrition source
- Antibacterial properties
- Dense albumen
- Chalaziferous layter
- Thin albumen
Fully formed Egg
What is Chalaza?
what does it do?
- Chalaza
- Twisted strands of ovomucin fibers
- “spring-like”
- Helps hold yolk steady in center of egg
Fully formed Egg
- Shell
How many
what are they called
what are they made of and what do they do?
- Two shell membranes
- Testa (inner shell membrane)
- an organic matrix with calcite, a crystalline form of calcium carbonate.
- Cuticle (outer shell membrane)
- Water repellent, reduces evaporation loss, forms a barrier for microorganisms
Fully formed Egg
- Shell
what is an “air cell”, where is it?
how is it shaped?
color?
what is it’s job?
- Air cell at blunt end
- Produced as egg cools after being laid
- Shape related to hen’s pelvis
- Color variations
- Mostly from 2 pigments
- Red-brown porphyrins
- Blue-green biliverdins
- Involved in gas exchange
Calcium metabolism
for eggshells
how much of the total body calcium is in a typical egg?
- Each egg typically represents ~10%-20% of the total body
calcium
Calcium metabolism
for eggshells
what are the 2 main sources of calcium?
- 2 main sources of calcium:
- Bone
- Dietary calcium
Calcium metabolism
for eggshells
what determines the relative importance of the calcium?
- The relative importance depends on the availability of dietary
calcium. - Diet contains 2% calcium, then medullary bone contributes
30% to 40% of the calcium - Bone contribution higher at night or lower calcium diets
Calcium metabolism
for eggshells
- The highly labile reservoir found in the medullary bone contains
enough calcium for…
- The highly labile reservoir found in the medullary bone contains
enough calcium for 1 egg
Calcium metabolism
for eggshells
Dietary calcium essential for….
- Dietary calcium essential for replenishing medullary bone
reservoir
Calcium homeostasis
- Regulated by what 4 things?
- Parathyroid hormone (PTH)
- Calcitonin
- Vitamin D3 (calcitriol)
- Sex hormones
Calcium homeostasis
regulation responses occur in ___ vs ____ in mammals?
- Responses within minutes vs hours in mammals
Calcium homeostasis
- Regulated by
- Parathyroid hormone (PTH)
produced where?
what is significant about the cells?
it promotes what?
how?
- PTH
- Produced by parathyroid gland
- Only chief cells, oxyphil cells absent
- Promotes calcium absorption from bone
- Induces rapid changes in calcium osteoclast activity
and calcium transfer by osteoblasts and osteocytes
Calcitonin and
ultimobranchial glands
* Calcitonin
where is it produced?
where is this located?
what 2 types of cells actively produce calcitonin? called? describe?
- Produced by ultimobranchial glands
- Anatomically distinct asymmetrical paired glands
positioned caudal to the parathyroid glands in the
thoracic inlet - 2 cell types (both actively produce calcitonin)
- Principal cells (similar to mammalian thyroid C-
cells) - Morphologically distinct endocrine cell type, with
larger intracytoplasmic granules
Calcitonin and
ultimobranchial glands
what is the role of calcitonin in avian calcium homeostasis
what is controversial about this and why?
- Role of calcitonin in avian calcium homeostasis is still
controversial - Stems from administration of calcitonin to eucalcemic
birds does not create hypocalcemia
Calcitriol
what is it? (composition)
what does it do?
how does it do it?
- Calcitriol (1,25-(OH)2-D3)
- Increases absorption of calcium across the duodenum
and jejunum wall - Mainly by calbindin
Calcitriol
combined with PTH it is responsible for….
- With PTH is responsible for calcium mobilization from
medullary bone
Calcitriol
why is it essential
what is a relevant about calcitriol in domestic foul?
how is it controlled?
- Appears essential for translocation of calcium across
the oviductal wall - Similar or identical calbindin protein is also present
in the distal portion of the uterus (oviduct) of
domestic fowl, with levels rising during egg laying - Note: it is believed that oviductal calbindin
production is controlled mostly by sex hormones
and not by 1,25-(OH)2-D3, as the production of the
intestinal calbindin
Sex hormones
Estrogen
what does it affect?
how is it related to calcium?
- Estrogen
- Affects calcium metabolism
- Mostly related to increased calcium storage,
mobilization, and transportation
Sex hormones
* Estrogen
- Increased estrogen causes…
under what condition can the source of calcium change?
what happens if calcitriol levels are insufficient?
where is it most prominently found?
where else can it be found?
- Increased estrogen causes osteoblasts to produce
medullary bone - Labile source of calcium when dietary supply
is insufficient - Complete mineralization can only occur if
calcitriol levels are adequate - Most prominent in the pelvic limb long bones
(femur and tibiotarsus) - Can also occur in the thoracic limb long
bones (humerus, radius, and ulna) and in
other areas
Sex hormones
* Estrogen
Decreased estrogen causes….
Decreased estrogen causes osteoblasts to
produce lamellar cortical bone (medullary bone
disappears)
Egg bound Lulu
in Lulus story, why was intramuscular injection in the legs avoided?
Although intramuscular injections in the legs are not routinely given in avian species, it is important to understand the function of the renal
portal system, particularly when using potentially nephrotoxic drugs or drugs that may be cleared by the kidneys.
