Week 6 Avian Anatomy & Physiology

Skin: Epidermis

Thin, flat epithelial cells that produce keratin

Skin: Dermis

• Thicker, tough fibrous connective tissue

• Storage for fat

• Smooth muscles innervate feather follicles

• Heat regulation

Glands

• No sweat glands in birds

• Uropygial gland = preen gland

• On dorsal surface at upper base of tail

• Secretes oily fatty substance

• Oil waterproofs feathers

• Varies in size with species

• Completely lacking in some species

Beaks

• Derivatives of a bird’s skin

• Upper and lower mandible covered with a horny keratin layer

  • Grows continuously

Claws

• Ends of each toe possessed horny sheath, derived from specialized scales

• Grows continuously

• Species differ in types of claws

  • Perching habits

  • Methods of procuring food

Feathers

• Outgrowths of skin

• Made of protein

  • Sensations only at the base

• Functions

  • Flight

  • Protection

  • Thermoregulation

  • Camouflage

  • Communication behaviors

• Location

  • Do not originate from the entire body

  • Overlap each other in the pterylae

  • Apteria are bare areas of skin

Contour Feathers

• Most visible

• Cover body and make up feathers of wings and tail

  • Commonly called remiges and retrices

Down Feathers

• Soft, fluffy

• Lack true shaft

• Under contour feathers next to the skin

• Molting

• Process of feather replacement

• Occurs in a species specific pattern

  • Allows bird to continue normal activities

• Usually replacement is symmetrical

  • One or two pairs of light feathers malted at a time

  • Major annual molt timed

• Increasing daily length, stimulates, pituitary, and thyroid glands to produce hormone that stimulate molting

Growth of Feathers

• Develop from papillae in feather tracts of dermis

• Newly developing feathers pushes old feathers out

• Feather emerges, covered by periderm

• Blood vessels from dermis reach into new feather (blood feathers; have blood and nerve supply)

• When feather is fully grown, blood dries up, and rachis is pinched closed

The System System

• Highly specialized framework to support both walking and flying

• Modifications allow for flight and walking

  • Reduction in number of bones

  • Fusion of some bones to form plates

  • Reduction in bone density

  • Loss of internal (cancellous) bone matrix

  • Bones are hollow and filled with air spaces

• The Avian Skeleton

• Axial Skeleton

  • Bones provide general framework of body

  • Skull, vertebral column, sternum (keel)

• Appendicular skeleton

  • Bones support locomotion

  • Wings, shoulder bones, legs, pelvic bones

• The skull

  • Bones thinner than in other animals

  • Jaws extend into keratinized bill

  • Large eye sockets bordered by sclerotic ring

  • Small portion of skull devoted to olfactory system

    • Poor sense of smell in most species

Vertebral Column

• Cervical vertebrae

  • Number greater than in mammals for greater flexibility

• Thoracic vertebrae

  • Rigid to provide strong support for rib cage

  • Uncinate process overlaps adjoining rear ribs

• Lumbar and sacral vertebrae

  • Fuse vertebrae from bony plate to support legs = synsacrum

• Coccygeal vertebrae

  • First human mobile to allow movement of tail feathers

  • Pygostyle = fused bony structure that supports tail feathers

Sternum (Keel)

• Large and concave

• Protects the chest

• Act as place or origin of flight muscles = keel

Pectoral (shoulder) Girdle

• 3 pairs of bones

• Coracoids, clavicles, scapulas

• Wing attaches to joint in glenoid cavity

Wings

• Joint at shoulder allows rotation in several planes

• Wing muscles attached at pectoral crest of humerus

  • Humerus longer and birds that glide and soar

• Joint at elbow, allows, movement only parallel to wing

• Patagium (propatagium) = web of skin

  • Extends from shoulder to wrist, assists in aerodynamics

• Alula bone originates from wrist

  • Carriers the alula feathers (steering feathers)

• Metacarpals bones join with fingers

  • Help support primary flight feathers

Pelvic Girdle

• Provides a rigid framework to support the legs

• Ilium, ischium, and pubis are paired bones joined where leg attaches to body

• Distal ends not fused to provide room for egg laying

Legs

• Femur attaches to pelvis at hip joint and is directed forward at knee

• Greater and lesser trochanters at side of muscle attachments

• Tibiotarsus and fibula

• Tarsometatarsus is the single bone of ankle (hock)

Feet

• Metatarsal pad

• Bottom of foot, surrounded by two, three, four toes

• Anisodactyl- one to faces to rear, other three face forward

• Zygodactyl- second and third toes face forward, first and fourth toes face backward