----start anat.lec.11.25.96

birds. this may be relevant on thanksgiving...

AMNIOTES
|
|-----mammals
|--->reptiles:lizards, crocs, alligators
 |
 |--->dinosaurs
 |
 |--->aves (birds)
though, some say birds directly from dinos.

BIRDS: endothermic, 4 chambered heart, closest living reptilian ancestor 
is crocodile, which also has 4 chambered heart, and birds also have large 
brains. have flight capability. but built mostly on REPTILIAN blueprint, 
with adaptations for FLIGHT and high levels of activity.

SKIN AND FEATHERS:
skin is paper thin and translucent, with feathers coming out of it. 
feathers are modified reptilian scales, and have three functions: FLIGHT, 
INSULATION, SEXUAL DISPLAY. 

bird basal metabolic temp about 40-41 degrees C. slightly higher than 
mammals. 
feathers are also extremely aeordynamic

 TYPES OF FEATHERS:

CONTOUR aka FLIGHT: a central shaft with asymmetric VANES on either side, 
made of tiny barbs coming diagonally off the central shaft. these barbs 
are covered with barbules which have hooks on them, holding them to the 
barbules of the next barb, so they stay together.

DOWN: look like contour feathers but smaller, less cohesive, closer to 
body...no barbules.

FEATHER TRACTS: PTERYLAE: see handout. this is where the feathers 
actually insert into the body. they are separated by bare areas of skin 
called APTERIA.

birds do not sweat, have no sweat glands, pant when hot. only external 
glands they have are

UROPYGIAL gland aka PREENING gland- a sebaceous gland at the birds butt, 
cranial to where the tailfeathers insert. creates an oily substance which 
the bird applies to feathers with its beak for waterproofing and 
smoothing of feathers.

NASAL SALT gland: situated in dorsal orbit, aids osmoregulation: 
basically desalinates water and secretes salt through the nose. an 
onboard desalination plant!

SKELETON: very very light. there are two reasons  for this...one, it's a 
weight saving adaptation (disputed), and two, it's a structural 
adaptation, along the lines of the sinuses in the horse skull. the bird 
bones have many spaces, mostly hollow, with simple column type supports 
within them.

NECK: mammals have 7 cervical vertebrae. reptiles/birds increase the 
number, not the length, of their vertebrae. chicken has about 14 cervical 
vertebrae. atlantooccipital joint is very flexible.

bird doesn't have the hypaxial muscles....most of thoracic vertebrae are 
fused into a structure called the NOTARIUM. then the remaining thoracic 
vertebrae, and all lumbar, sacral vertebrae, and a couple caudal 
vertebrae fuse into the SYNSACRUM- which is fused to the pelvis. finally, 
the last few caudal vertebrae fuse into the PYGOSTYLE which supports tail 
feathers and the uropygial gland.

PELVIS:
see diagram. the acetabulum is perforate (has a hole) and the pelvis is 
open ventrally.

the STERNUM: is keeled, like the base of a ship. the keeled part is 
called the carina, and that's where the flight muscles attach. it is 
attached to ribs which attach to the notarium and which have uncinate 
processes. the coracoid bone meets the c-spine from the cranial aspect of 
the sternum, and the furcula is cranial to the coracoid and is analagous 
to the clavicle - you know this as the wishbone.

PELVIC LIMB
the FEMUR has nutrient foramen
the PATELLA
the TIBIOTARSUS: fusion of tibia and prox tarsal bones
the TARSOMETATARSUS: fusion of distal tarsal bones with metatarsals I, 
II, III

digits II, III, IV come off cranially, and I comes off caudally. V is 
gone.

THORACIC LIMB
the HUMERUS - has nutrient foramen and PNEUMATIC DIVERTICULUM - air 
filled space inside the bone. bird could breathe through it even 
w/trachea sealed if it were opened to the outside.
RADIUS
ULNA
CARPOMETACARPUS: fusion of carpal and metacarpal bones.
digit II (ALULA, BASTARD WING) comes off near the ulna, and III is the 
most distal, and IV is near III. the primary feathers come off over III 
and IV and carpometacarpus, and secondary feathers come off over the 
ulna.

MUSCLES: 
two most important muscles: PECTORALIS: lowers the wing, originates on 
keel of sternum, inserts on humerus. the SUPRACORACOIDEUS lies between 
pectoralis and sternum, then it's tendon goes through a foramen called 
the triosseal foramen, in the shoulder, to get to the top of the wing. 
the foramen is formed by scapula, coracoid, and furcula

CIRCULATORY SYSTEM:

HEART: four chambers
AORTIC ARCH: goes to the right
Has both RIGHT and LEFT BRACHIOCEPHALIC ARTERY and R and L VENA CAVA.
Two PORTAL SYSTEMS: hepatic and renal.

birds have no lymph nodes, except they do have extensive diffuse 
lymphatic tissue.

RESPIRATORY SYSTEM:
vultures have been observed at 38,000 feet, flying (unfortunately, we 
know that altitude because that's where the plane ran into it.)
birds have NO diaphragm, so thoracoabdominal cavity is continuous. 
TRACHEAL RINGS are complete. the LARYNX has only a cricoid and arytenoid 
cartilage. sound is produced in the SYRINX.

follow the trachea to the bifurcation and there is a thinning and some 
ridges and that's where sound is produced. only males vocalize. females 
will if you give them testosterone.

the lungs are just ventral to the vertebral column and are responsible 
for UNIDIRECTIONAL ventilation. they are connectd to a bunch of cranial 
and caudal air sacs. the air sacs are responsible for pumping air in and 
out through the lung. gas exchange takes place in PARABRONCHI and air is 
passed caudal to cranial. birds need two breaths to fully circulate air 
through the respiratory system.

DIGESTIVE TRACT
birds for the most part have no teeth - fossil birds do have teeth. 

at the end of the esophagus there is a diverticulum called a CROP - in 
pigeons and doves they make "crop milk" there and regurgitate it w/food 
to feed to the young. crop- storage space.

the stomach: glandular proventriculus and muscular region called gizzard. 
the gizzard is what does most of the "chewing" via muscular contractions. 
there is usually some GRIT - stones, sand- in there.

there are PAIRED CECAE.

then there is a cloaca - common chamber into which digestive, urinary, 
and reproductive products empty. see figure 39-15 on handout.

when male bird mates, the ventral vent everts and performs "cloacal kiss" 
emptying sperm into female cloaca. this is in fowl. in some other birds 
there is an intromittent phallus which is just a larger part of the vent 
that actually goes into the female's proctodeum.



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