Comparative anatomy involves comparing the body structures of different species to understand evolutionary relationships and adaptations. There are three key types of structures studied in comparative anatomy: homologous structures which are similar due to common ancestry; analogous structures which evolve independently but serve similar functions; and vestigial structures which were useful ancestrally but no longer serve a purpose. Comparative anatomy across species can provide insights into anatomy and physiology, evolutionary history, and help address issues like animal health and conservation.

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

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)

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. ■ Vertebrate
embryos are
structurally
similar in early
embryonic
stages.

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

17. Caudal Cranial
Dorsal
Ventral

19. 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)

20. 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

21. DOR:čšAŁ Ø O O Y C A V I T V

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

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

28. 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.
●

29. 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

30. Higher Classification of Chordata
●Phylum Chordata
●Subphylum Urochordata – tunicates, sea
squirts
●SubphylumCephalachordata – lancelets
●Subphlum Vertebrata- vertebrates

31. ●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
Vertebrate Higher Classification

32. 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

33. 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.

34. 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

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

36. Endoskeleton

37. Exoskeleton

38. 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)

39. Classification of Bones on the Basis of Shape

40. Cartilage – Characteristics
●Mostly water; no blood vessels or nerves
● Tough, resilient
●New cartilage forms from
chondroblasts
● Heal poorly

41. 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

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

44. Hinge joint

47. Human
Skeleton
● 206 Bones
●Axial skeleton: (80 bones)
in skull, vertebrae, ribs,
sternum, hyoid bone
●Appendicular Skeleton:
(126 bones)- upper & lower
extremities plus two girdles
●Half of bones in hands &
feet

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

50. Axial skeleton Appendicular
skeleton

52. 7Cervical
Vertebras
13Thoracic
Vertebras
6Lumbar
Vertebras
5Sacral
Vertebars
18-20
Coccygial
vertebras

56. 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.

57. 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.

59. 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

60. 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.

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

64. Bird
66