Comparative anatomy involves comparing the body structures of different species to understand evolutionary relationships and physiological similarities and differences. The document discusses key topics in comparative anatomy including homologous and analogous structures, directional terms, skeletal systems in humans and other vertebrates like fish, birds and cattle. Examples are provided of skeletal features like pneumatic and medullary bones that are specialized adaptations for respiration and calcium storage.

1. Comparative anatomy
( Chordates)
Skeletal system
1-Human
2-Ruminant
3-Avian
4-Horse
5-Fish
Dr.Omer

2. Comparative Anatomy
involves comparing the body structures of species
 is the study of differences and similarities in
the anatomy of different species .
 It is closely related to evolutionary biology and
phylogeny .

3. Concepts
Phylogeny: (inheritance) the history of the evolution of
a species or group, especially in reference to lines of descent
and relationships among broad groups of organisms
Evolution: (modification and inheritance) evolution is the
change in the characteristics of a species over several
generations and relies on the process of natural selection
Convergence: found in distantly related groups; evolved
independently.
Parallelism: found in closely related groups; evolved
independently.

4. Comparative anatomy Includes:
• Change, adaptation, and mutation of species
• The invasion of new territories
• Species compatibility with surroundings

5. How can comparative anatomy
help us?
1-Understand our history
2- Show how organisms function
3-Consider plans for change
4-How they develop
5-Improve animal genetics
6-Preserve endangered species

6. Why should we be aware of
comparative anatomy?
Variations in care for animals
Differences in animal habits

7. Structural development
Homologous Structures
Analogous Structures

8. Homologous structures
Are structures that are similar in two organisms because
they have a common ancestor
Organs with similar structure but different functions are
called Homologous structures
Bones in the forelimb of the human, whale, cat, bat, bird
are used for vastly different movement, they all have
remarkably similar structure and organization (bones,
nerves, blood vessels)
This indicated common ancestry (DNA)

10. Homologous Structures (BONES in the FORELIMBS)Homologous Structures (BONES in the FORELIMBS)

11. Analogous structures
• Features of different species that are similar in
function but are structurally different
• Do not have a common ancestry
• Evolved due to a similar environmental challenge
• Ex) Birds & insects have wings to fly although their
wing structure is different
• Analogous structures are caused by convergent
evolution. In convergent evolution, two species
evolve the same traits to adapt to an environment side
by side, but they didn't come from the same ancestor

12. Analogous Structures
E.g. Bird wing and
insect wing

13. Embryology
• Humans have pouches in early development
• In fish these pouches develop into gill slits
• In humans they form the eustachian tube and auditory
canal.
• Human embryo has a tail and body hair like embryos
of all other mammals but in the human embryo these
features disappear before birth

14.  VertebrateVertebrate
embryos areembryos are
structurallystructurally
similar in earlysimilar in early
embryonicembryonic
stages.stages.

16. Directional Terms
Used to describe the positions of structures on the
body relative to other structures or locations

17. DIRECTIONAL TERMSDIRECTIONAL TERMS
Definition of terms:
Anterior (cranial) toward the head
Posterior (caudal) toward the tail
Cranial head region
Caudal pertaining to the tail region
Dorsal toward the back (top) of the animal
Ventral toward the belly of the animal
Medial toward the median line
Distal away from the center or origin
Proximal toward the center or origin

18. Caudal Cranial
Dorsal
Ventral

20. REGIONAL NAMES
These names are given to specific regions of the body for reference.
Examples:
 Cranial (skull),
 Thoracic (chest),
Brachial (arm),
Patellar (knee),
Cephalic (head),
 Gluteal (buttock)

21. Body Cavities
Ventral body cavity
Contains most of the soft organs; divided by thin
diaphragm
 Thoracic cavity- heart, lung, esophagus, blood vessels
 Abdominal cavity- digestive tract
 Pelvic cavity- urinary organs, reproductive organs
Dorsal body cavity
Contains the brain and spinal cord
 Cranial cavity- brain
 Spinal cavity- spinal cord

24. Spinal
Cavity
Dorsal
Cavity
Ventra
l
Cavity
Abdominal
Cavity
Diaphragm
Thoracic
Cavity
Cranial
Cavity

25. Chordates
All chordates have the following features at some stage in
their life (in the case of humans and many other
vertebrates, these features may only be present in the
embryo):
Notochord
Dorsal Hollow Nerve Cord
Pharyngeal slits
Post-anal tail


26. Characteristics of the Chordates
Notochord, dorsal hollow nerve cord, pharyngeal gill
slits, blocks of muscle, postanal tail

29. Pharyngeal Slits
Pharyngeal slits are openings in the pharynx (the region just
posterior to the mouth) that extend to the outside environment
. In organisms that live in aquatic environments, pharyngeal slits
allow for the exit of water that enters the mouth during feeding.
Some invertebrate chordates use the pharyngeal slits to filter food
out of the water that enters the mouth.
In vertebrate fishes, the pharyngeal slits develop into gill arches, the
bony or cartilaginous gill supports.
In most terrestrial animals, including mammals and birds,
pharyngeal slits are present only during embryonic development. In
these animals, the pharyngeal slits develop into the jaw and inner
ear bones.


30. Post-anal Tail
The post-anal tail is a posterior elongation of the body,
extending beyond the anus.
The tail contains skeletal elements and muscles, which
provide a source of locomotion in aquatic species.
 In some terrestrial vertebrates, the tail also helps with
balance, courting, and signaling when danger is near.
 In humans and other apes, the post-anal tail is present
during embryonic development, but is vestigial as an adult

31. Blocks of Muscle - Myotomes
• Surrounding the notochord and nerve cord are blocks of
muscle - myotomes

32. Higher Classification of Chordata
Phylum Chordata
Subphylum Urochordata – tunicates, sea squirts
Subphylum Cephalachordata – lancelets
Subphlum Vertebrata- vertebrates

33. Vertebrate Higher ClassificationSuperclass Agnatha - without jaws
Class Myxini – hagfishes
Class Cephalaspidomorphi – lampreys
Superclass Gnathostomata – with jaws
Class Chondrichthyes – sharks, rays,
chimaeras(Cartilaginous fishes)
Class Actinopterygii – ray-finned fishes
Class Sarcopterygii – lobe-fin fishes
Class Amphibia – frogs, salamanders
Class Reptilia – snakes, lizards, crocodiles
Class Aves - birds
Class Mammalia - mammals

34. skeletal system
The skeletal system consists of the bones and joints
along with the cartilage and ligaments that occur at
the joints.
Bones: Hard Tissue, mostly calcium phosphate and
calcium carbonate, provides support and makes Red
Blood Cells
Ligaments: Strong, white bands of tissue that connect
two bones together at a joint

35. skeletal system
Cartilage: Hard tissue that prevents bones from
grinding against each other.
Joints: Location of where two or more bones meet.
Tendon: Connects muscle to bone.

36. Skeletal System - Functions
Provides the frame and support for all the other
systems and organs
Aids in movement
Provides protection
Site of mineral storage
Site of blood cell formation
Made up of bones,
cartilage, and
connective tissue

37. Two types of skeleton
Exoskeleton (protective structure on the
outside of the body)
Endoskeleton (protective structure on the
inside of the body)

38. Endoskeleton

39. Exoskeleton

40. Types of Bone
Long bones: longer than they are wide; shaft & 2 ends
(e.g.: bones of arms & legs,except wrist, ankle &
patella)
Short bones: roughly cube-shaped (e.g.: ankle & wrist
bones)
Sesamoid bones: short bones within tendons (e.g.:
patella)
Flat bones: thin, flat & often curved (e.g.,: sternum,
scapulae, ribs & most skullbones)
Irregular bones: odd shapes; don't fit into other
classes (e.g.: hip bones & vertebrae)

41. Classification of Bones on the Basis of ShapeClassification of Bones on the Basis of Shape

42. Cartilage – Characteristics
Mostly water; no blood vessels orMostly water; no blood vessels or
nervesnerves
Tough, resilientTough, resilient
New cartilage forms fromNew cartilage forms from
chondroblastschondroblasts
Heal poorlyHeal poorly

43. Types of Cartilage
Hyaline Cartilages: fine collagen fiber matrix- most
abundant type- found in articular (movable joint)
cartilages, costal cartilages (connect ribs to sternum),
respiratory cartilages (in larynx & upper respiratory
passageways) & nasal cartilages
Elastic Cartilages: similar to hyaline cartilage, more
elastic fibers (very flexible) – found in external ear &
epiglottis (larynx covering)
Fibrocartilage: rows of chondrocytes with thick
collagen fibers; highly compressible with great tensile
strength- found in menisci of knee, intervertebral discs
& pubic symphysis

44. Types of Joint
There are 4 types of joints :
Hinge
Knee
Ball and Socket
Hip
Gliding
Vertebrae
Fixed ( Cartliaginous)
Skull

46. Hinge joint

49. Human
Skeleton
206 Bones206 Bones
Axial skeletonAxial skeleton: (80 bones): (80 bones)
in skull, vertebrae, ribs,in skull, vertebrae, ribs,
sternum, hyoid bonesternum, hyoid bone
Appendicular SkeletonAppendicular Skeleton::
(126 bones)- upper & lower(126 bones)- upper & lower
extremities plus two girdlesextremities plus two girdles
Half of bones in hands &Half of bones in hands &
feetfeet

50. Skull
Sternum
Ribs
Vertebral
column
Metatarsals
Metacarpals
Phalanges
Clavicle
Scapula
Humerus
Radius
Pelvis
Ulna
Carpals
Femur
Patella
Fibula
Tibia
Tarsals
Phalanges
The Skeletal System
Section 36-1
Axial
Skeleton
Appendicular
Skeleton

52. Axial skeleton Appendicular
skeleton

54. 7 Cervical
Vertebras
13 Thoracic
Vertebras
6 Lumbar
Vertebras
5 Sacral
Vertebars
18-20
Coccygial
vertebras

58. Pneumatic bones
The pneumatic bones are important to the
chicken for respiration.
They are hollow bones
connected to the chicken’s respiratory system and are
important for the chicken
Examples of pneumatic bones:
skull, humerus, clavicle, keel(sternum)
pelvic girdle
lumbar and sacral vertebrae.

59. Medullary bones
The medullary bones are an important source of calcium
for the laying hen.
Calcium is the primary component of egg shells and a hen
Mobilizes 47% of her body calcium to make an egg shell.
Examples:
tibia, femur, pubic bones, ribs, ulna, toes, and scapula.

61. Fish skeletal system
 The function of the skeletal system is one of support.
Skeletal tissues:

Axial skeleton:
 Head, trunk, and tail regions.
Head:
Trunk skeleton: modified portion of the vertebral
column.
Tail skeleton: remainder of the vertebral column

62. Fin :To allow the fish to stay upright, move, and maneuver in the water.
Rays : soft cartilage structure that supports the fins of the fish.
Tail Fin : Helps to propel the fish
Dorsal and Anal Fins : balance and close quarters movements.
Pectoral Fin : allows to fish to dive and also allows the fish to stay in
one spot.
Pelvic Fin : balances and positions .
Lateral Line : helps the fish detect vibration, sensors, and helps the fish
to find food and to navigate to avoid predators.

65. Cattle Sheep Horse Humans Poultry
Cervical 7 7 7 7 14
Thoracic 13 13-14 18 12
Lumbar 6 6-7 6 5
Sacral 5 4 5
(fused)
5
(fused)
Coccygeal 18-20 16-18 4
(fused)
6
Number of Vertebrae in Selected Animal Species

66. Bird
66