Comparative Anatomy of Vertebrate Skeletal and Muscular Systems

Posted on Aug 24, 2024 in Biology

Muscle

Connective Tissue in Muscles

1. Identify these special connective tissue terms associated with muscles: fascia, raphe, tendons & myosepta.

• Fascia: Helps distribute blood vessels throughout the muscle.
• Raphe: A line of connective tissue that serves as a connection point between muscles.
• Tendons: Connective tissue surrounding the muscle that directly attaches muscles to bones.
• Myosepta: Connective tissues between myomers, linking them together.

Muscle Function and Classification

2. Why is it that muscles can only pull?

Muscles cannot actively extend beyond their resting length; they can only contract (pull).

3. How is muscle generally classified?

Muscles are generally classified by: Location, Function, Shape, Direction of fibers, Number of attachments, and Divisions.

Cranial Nerves and Muscle Evolution

4. Why are cranial nerves used to establish common evolutionary origin in the muscles of the head and throat?

Cranial nerves exhibit a high degree of fidelity with their associated musculature. Their evolutionary history can be traced back to ancestral pharyngeal arches, providing insights into the development of head and neck muscles.

Muscle Actions

5. Review: Understand & be able to use the terms for muscle actions e.g. flexion, extension, abduction, etc.

Refer to diagrams and resources for a comprehensive understanding of muscle actions such as flexion, extension, abduction, adduction, rotation, etc.

Shark Muscle Anatomy

6. Learn 1 origin & 1 insertion point for each shark muscle in the evolutionary origins table.

(Refer to the evolutionary origins table for specific origins and insertions of shark muscles.)

7. Learn at least 1 action for each shark muscle in the evolutionary origins table.

(Refer to the evolutionary origins table for specific actions of shark muscles.)

Comparative Muscle Anatomy

8. Know which muscles perform the same functions in the shark, necturus and cat.

(Refer to”Muscle Notes ” on Page 11 for a comparison of muscle functions across different species.)

9. Know the evolutionary origin of each shark muscle in the evolutionary origins table & name a cat muscle with the same origin: (Hint: look at the colored cat)

• a. Epaxial & Hypaxial: (Refer to the evolutionary origins table and anatomical illustrations.)
• b. Appendicular: dorsal or ventral & pectoral or pelvic. (Refer to the evolutionary origins table and anatomical illustrations.)
• c. Hypobranchial (Refer to the evolutionary origins table and anatomical illustrations.)
• d. Branchiomeric arch 1, Branchiomeric arch 2 & Branchiomeric Arch 3-7 (Refer to the evolutionary origins table and anatomical illustrations.)

Bipedalism and Human Muscle Evolution

10. What changes happened in human muscles due to bipedalism?

Key changes in human muscles due to bipedalism include:

• Gluteus Maximus: Became larger and more prominent.
• Gluteus Medius: Became shorter and positioned for stability.
• Gluteus Minimus: (Refer to resources for specific changes.)
• Upper Body Muscles: Adaptations for balance and weight-bearing on the limbs.
• Connection between Head and Shoulders: Modifications for upright posture.
• Pectoral Muscles: Lengthening to facilitate arm swing.
• Achilles Tendon and Gastrocnemius: Enhanced for walking and running.

Skull

Components of the Skull

11. Compare the general features of the three components of the skull including where they derive from developmentally. How does bone formation in the dermatocranium differ from bone formation in the chondrocranium/neurocranium and splanchnocranium?

• Occipital Bones: Derived from vertebrae (mesoderm/mesenchyme).
• Dermatocranium (Mesenchyme): Forms the outermost casing of the brain. It originated from the bony armor of ancient fishes. Bone formation occurs through intramembranous ossification, a process that directly converts mesenchymal tissue into bone without a cartilaginous intermediate.
• Chondrocranium: Encases the brain and sensory organs. It develops from neural crest cells and mesodermal mesenchyme. Bone formation follows endochondral ossification, involving a cartilaginous precursor that is gradually replaced by bone.
• Splanchnocranium: Arises from neural crest cells and contributes to both cartilaginous and bony structures. It originates from the pharyngeal arches, which initially support the gills in ancestral vertebrates. In later evolution, these arches contribute to the jaws, hyoid bone, and middle ear ossicles. Bone formation primarily occurs through endochondral ossification.

Evolution of the Splanchnocranium

12. How did the splanchnocranium evolve from the pharynx of early chordates? How did it become parts of the middle ear?

The splanchnocranium evolved from the pharyngeal arches that supported the gills in early chordates. The first arch gave rise to the jaws, while the second arch (hyoid arch) contributed to structures like the hyoid bone, stapes (a middle ear bone), and parts of the temporal bone.

The transition of splanchnocranium elements into the middle ear is a key evolutionary event in vertebrates. The hyomandibular bone, initially involved in jaw support, became the stapes, transmitting sound vibrations from the eardrum to the inner ear.

The Hyoid Bone

13. What is the role of the hyoid bone? Where does it derive from?

The hyoid bone, derived from the second pharyngeal arch, plays a crucial role in supporting the tongue, facilitating swallowing, and anchoring muscles involved in speech.

Bones of the Chondrocranium

14. What are the three main bones that are part of the chondrocranium/neurocranium in humans? How did these three bones evolve? (simple explanation).

The three main bones of the human chondrocranium are:

• Sphenoid: Formed from the fusion of several embryonic bones, including the basisphenoid, presphenoid, and orbitosphenoids.
• Ethmoid: Contributes to the nasal cavity, eye sockets, and the nasal septum.
• Occipital: Forms the back and base of the skull, encompassing the foramen magnum (where the spinal cord connects to the brain).

These bones evolved through a complex process of fusion and modification of ancestral cartilaginous elements in the vertebrate lineage.

Composite Bones of the Skull

15. Which are the three composite bones of the human skull?

The three composite bones of the human skull are:

• Occipital: Formed from the fusion of both endochondral (chondrocranium) and intramembranous (dermatocranium) bones.
• Temporal: A complex bone formed from the fusion of several parts, including the squamous, petrous, and tympanic parts.
• Sphenoid: Also a composite bone, formed from the fusion of several embryonic bones.

Comparison of Dermatocranium

16. Compare the dermatocranium of alligator and human

The alligator dermatocranium consists of multiple bones, including several individual occipital elements. In contrast, the human dermatocranium features a single, fused occipital bone. This difference reflects the evolutionary trend towards skull simplification and increased fusion in mammals.

Mandibular Attachment

17. Compare the mandibular attachment found in bony fish, sharks, crocodiles, and mammals.

• Bony Fish: Hyostylic jaw suspension, where the mandibular arch is attached to the braincase via the hyomandibular bone.
• Sharks: Amphistylic jaw suspension, with the jaw connected by a ligament to the skull.
• Crocodiles: Metautostylic jaw suspension, where the jaw articulates with the quadrate bone, which is firmly attached to the skull.
• Mammals: Craniostylic jaw suspension, with the dentary bone (lower jaw) articulating directly with the temporal bone of the skull.

Kinetic vs. Akinetic Skulls

18. What is the difference between a kinetic and akinetic skull? What are three examples of each?

• Kinetic Skull: Allows for movement between the upper jaw and the braincase. Examples include: Snakes, Lizards, and Birds.
• Akinetic Skull: Characterized by a rigid connection between the upper jaw and the braincase. Examples include: Turtles, Crocodiles, and Mammals.

Skull and Teeth

Comparison of Alligator and Human Skulls

19. For lab/lecture combo, you should be able to compare, contrast, and learn the major alligator and human skull bones. You should be able to find the corresponding bones and fenestra between specimens.

(Refer to anatomical diagrams and resources for a detailed comparison of alligator and human skulls.)

Fenestra in Synapsid Skulls

20. What is the role of the fenestra in synapsid skulls?

Fenestrae (openings) in synapsid skulls, the lineage that includes mammals, provided space for the attachment of jaw muscles, allowing for greater bite force and diversification of feeding strategies.

Sound Transmission in Reptiles and Mammals

21. How is sound changed from a mechanical pulse into information in the brain in reptiles and mammals? When relevant, Talk about the ear canal, middle ear, and inner ear.

Reptiles: Sound waves are transmitted through the tympanic membrane (eardrum) to the inner ear via a single middle ear bone, the stapes. The stapes vibrates against the oval window of the inner ear, setting the fluid inside in motion. These fluid vibrations are then converted into electrical signals by hair cells in the cochlea, which are sent to the brain for interpretation as sound.

Mammals: Possess a more complex middle ear with three bones: the malleus, incus, and stapes. These bones act as a lever system, amplifying sound vibrations from the eardrum to the oval window. The inner ear functions similarly to that of reptiles, with hair cells in the cochlea converting fluid vibrations into electrical signals.

Tooth Classification

22. Can you classify teeth according to their variability in the jaw, the number of cusps, and how many replacement sets of teeth a vertebrate can get, and their attachment system?

• Tooth Variability:
  • Homodont: Teeth are similar in shape and size throughout the jaw (e.g., most reptiles).
  • Heterodont: Teeth vary in shape and size, reflecting specialization for different functions (e.g., mammals).
• Tooth Replacement:
  • Polyphyodont: Teeth are continuously replaced throughout life (e.g., most fishes and reptiles).
  • Diphyodont: Two sets of teeth: deciduous (baby) teeth and permanent teeth (e.g., mammals).
  • Monophyodont: Only one set of teeth throughout life (e.g., some mammals like platypuses).
• Tooth Attachment:
  • Thecodont: Teeth are set in sockets within the jawbone (e.g., mammals, crocodilians).
  • Acrodont: Teeth are attached to the crest of the jawbone (e.g., some lizards).
  • Pleurodont: Teeth are attached to the inner side of the jawbone (e.g., snakes, some lizards).

Dental Formulae

23. Can you calculate the dental formulae of a mammalian skull?

Dental formulae represent the number of each type of tooth (incisors, canines, premolars, molars) in one-half of the upper and lower jaws. For example, the dental formula for a dog is:

I 3/3, C 1/1, PM 4/4, M 2/3

This indicates that a dog has 3 incisors, 1 canine, 4 premolars, and 2 molars on one side of the upper jaw, and 3 incisors, 1 canine, 4 premolars, and 3 molars on one side of the lower jaw.

Axial Skeleton

Cartilage vs. Bone

24. Compare and contrast the characteristics of cartilage and bone

Both cartilage and bone are connective tissues that provide support and structure to the body. However, they differ in their composition, properties, and functions.

Types of Cartilage

25. Which are the different types of cartilage and where can they be found?

• Hyaline Cartilage: The most common type, found in the ribs, nose, larynx, trachea, and articular surfaces of joints.
• Fibrocartilage: Provides strength and support, found in intervertebral discs, joint capsules, and ligaments.
• Elastic Cartilage: Provides flexibility and resilience, found in the external ear, epiglottis, and parts of the larynx.

Parts of a Long Bone and Bone Healing

26. What are the parts of a long bone? Why do bones break and how do they heal?

• Epiphysis: The rounded end of a long bone.
• Metaphysis: The region between the epiphysis and diaphysis, containing the growth plate in growing bones.
• Diaphysis: The shaft or central part of a long bone.

Bones break due to excessive force or stress. Bone healing involves a complex process of inflammation, repair, and remodeling, ultimately restoring the bone’s structure and function.

Terrestrial Locomotion and Vertebrae

27. How does terrestrial locomotion affect evolution of vertebrae?

Terrestrial locomotion led to significant changes in vertebrae, including:

• Enlargement of specific vertebral elements for weight-bearing.
• Regional differentiation of vertebrae for specialized functions (e.g., cervical, thoracic, lumbar, sacral).
• Strengthening of the vertebral column for support and locomotion on land.

Rib Evolution

28. Describe the main evolutionary changes in the ribs of fish vs. tetrapods and mammals.

• Fish: Ribs primarily provide support and muscle attachment along the body wall.
• Tetrapods: Ribs became more robust and differentiated into regions (e.g., cervical, thoracic, lumbar) to support the weight of the body on land and aid in breathing.
• Mammals: Ribs are further specialized, with the thoracic ribs forming a rib cage that protects the lungs and heart.

Axial Skeleton Specializations

29. Compare and contrast the main specializations of the axial skeleton in snakes, birds and mammals (you will need to identify their vertebrae in lab).

• Snakes: Highly flexible vertebral column with additional articulations for enhanced mobility.
• Birds: Fusion of vertebrae in the trunk region (synsacrum) for stability during flight, and a flexible neck with heterocoelous vertebrae.
• Mammals: Seven cervical vertebrae, a variable number of thoracic and lumbar vertebrae, and fused sacral vertebrae for pelvic girdle attachment.

Mammalian Vertebral Column

30. What are the typical regions of the vertebral column in mammals? Describe what they are, and how many vertebrate in each

• Cervical: Neck region, 7 vertebrae.
• Thoracic: Chest region, 12 vertebrae in humans (number can vary in other mammals).
• Lumbar: Lower back region, 5 vertebrae in humans.
• Sacral: Fused vertebrae forming the sacrum, which articulates with the pelvic girdle.
• Coccygeal: Tail region, variable number of vertebrae (fused in humans to form the coccyx).

Specialized Cervical Vertebrae

31. What are the specializations of the first two cervical vertebrae in tetrapodes? What type of joint do they form?

The first two cervical vertebrae, the atlas (C1) and axis (C2), are specialized for head movement. The atlas articulates with the skull, forming a pivot joint that allows for nodding and tilting of the head. The axis has a prominent dens (odontoid process) that articulates with the atlas, enabling rotational movement of the head.

Vertebrae Labeling

32. Can you label the main parts (centrum, neural and hemal arches, zygapophysis and transverse processes) of vertebrae? Can you draw a typical vertebrae with its parts?

(Refer to anatomical diagrams and resources for labeling and drawing vertebrae.)

Appendicular Skeleton

Fin-Fold Theory

33. What is the fossil, developmental and molecular support for the fin fold theory for the origin of paired fins?

The fin-fold theory proposes that paired fins (pectoral and pelvic) in vertebrates evolved from lateral folds of skin and muscle along the body wall of ancestral chordates. Fossil evidence, developmental studies, and molecular analyses support this theory.

Terrestrial Locomotion and Girdles

34. How does terrestrial locomotion affect the pectoral and pelvic girdles?

Terrestrial locomotion led to significant changes in the pectoral and pelvic girdles, including:

• Strengthening and reinforcement of the girdles to support the weight of the body on land.
• Attachment of the pelvic girdle to the vertebral column for stability.
• Loss of the connection between the pectoral girdle and the skull, allowing for greater head mobility.

Evolution of Pectoral and Pelvic Girdles

35. Describe the main evolutionary changes in the pelvic and pectoral girdles of fish vs. tetrapodes and mammals.

• Fish: Pectoral girdle attached to the skull, pelvic girdle not directly attached to the vertebral column.
• Tetrapods: Pectoral girdle detached from the skull, pelvic girdle attached to the vertebral column.
• Mammals: Further modifications to the girdles for specific locomotor adaptations.

Specializations of the Appendicular Skeleton

36. Compare and contrast the main specializations of the appendicular skeleton in birds and mammals.

• Birds: Wings modified for flight, fusion of bones in the hand and wrist, lightweight bones with air spaces.
• Mammals: Limbs adapted for various forms of locomotion (e.g., running, climbing, swimming), diverse hand and foot structures.

Bones of the Girdles

37. What are the bones of the pectoral and pelvic girdles in vertebrates? Can you label them in a drawing?

(Refer to anatomical diagrams and resources for labeling the bones of the pectoral and pelvic girdles.)

Variation in the Manus

38. Can you describe the variation from the general pattern in the manus in 3 different vertebrates?

(Provide specific examples of manus (hand) variations in three different vertebrates.)

Sprawled vs. Cursorial Locomotion

39. Compare and contrast locomotion and pelvic/pectoral girdle in a sprawled posture (e.g. alligator) and a eutherian mammal with cursorial locomotion.

• Sprawled Posture (e.g., Alligator): Limbs project laterally from the body, providing stability but limiting speed. The pectoral girdle is robust, and the pelvic girdle is attached to the vertebral column.
• Cursorial Locomotion (e.g., Horse): Limbs are positioned beneath the body, allowing for efficient, high-speed running. The girdles are adapted for this type of locomotion.

Types of Terrestrial Locomotion

40. What are the different types of terrestrial locomotion?

• Cursorial: Running.
• Saltatorial: Jumping or hopping.
• Scansorial: Climbing.
• Fossorial: Digging.

Stride Length and Stride Rate

41. Explain how stride length and stride rate help an animal increase running speed.

Stride length is the distance covered in a single stride, while stride rate is the number of strides per unit of time. Increasing either stride length or stride rate, or both, will increase running speed.

Unguligrade Locomotion

42. How do unguligrades benefit from a longer limb?

Unguligrades, animals that walk on the tips of their toes (hooves), benefit from longer limbs as they increase stride length, allowing for faster running speeds.