Biol 410comparative Vertebrate Anatomyspring 2020assignment Muscular ✓ Solved

BIOL 410 Comparative Vertebrate Anatomy Spring 2020 Assignment : Muscular System Case Study Overview : The study of comparative anatomy often comes with the need to appreciation the physiological functions of the anatomical structures that we our examining. In doing so, we can better understand how variations in anatomical form determine function for chordates. This week, you have reviewed adaptations & similarities in the muscular system of fish, reptiles, amphibians, birds, and mammals. I have included a comparative illustration of three mammalian species below (dog, human, and horse). Note that the temporalis and masseter muscles have been identified in each of the illustrations.

The temporalis and masseter muscles perform an important role in the chewing (mastication) process of mammals. These muscles not only help with ripping and tearing of food, but they also help with the grinding process at the jaw joint (temporomandibular joint). Task : Observe the size and shape of the temporalis and masseter muscles of the mammalian species illustrated below. Hypothesize why the size, shape, and attachment sites differ between the animals. How do these adaptations assist with the chewing process of each animal?

Then, provide supporting evidence to support your hypothesis using 2-3 scholarly resources. Length : 1-2 pages, 12-point font, double-spaced Format : APA citation Dogs have a huge temporalis muscle for snapping the jaw closed. Dog requires huge force to shut the jaws, so the point of articulation of temporomandibular joint is level with the teeth.

Paper for above instructions

Comparative Analysis of the Temporalis and Masseter Muscles in Dogs, Humans, and Horses

The study of the muscular system across various mammalian species illuminates the evolutionary adaptations that have optimized food intake and processing among different animals. In particular, the temporalis and masseter muscles play critical roles in the mastication process, which involves not only the mechanical breakdown of food but also the preparation of this food for digestion. This paper aims to analyze the differences in size, shape, and attachment sites of the temporalis and masseter muscles in dogs, humans, and horses, with a focus on their functional implications for the chewing process in each species.

Anatomical Differences Among Species

Size and Shape

The temporalis muscle is notably large and robust in dogs, adapted for significant force generation required for their predatory chewing habits. Dogs possess powerful jaws equipped with large canine teeth intended for ripping flesh. The position of the temporalis muscle, particularly its attachment at the coronoid process of the mandible, enables a stronger leverage effect (Weijs, 1989). In comparison, the temporalis muscle in humans is comparatively smaller, reflecting a diet that is less reliant on tearing and more on grinding and processing food (Hiiemae et al., 1991). The human masseter is also prominently developed, albeit its overall requirement is less intense than in dogs.
In horses, the masseter muscle is especially vast and laterally positioned, as their diet consists of fibrous plant materials. This positioning helps in the grinding of grass and hay, which is critical for proper digestion (Mason, 2006). Unlike the dog, the horse's biting action focuses more on lateral movement, as opposed to the vertical snapping action seen in dogs.

Attachment Sites

The attachment sites of the temporalis and masseter muscles significantly affect their functional roles. In dogs, the temporalis muscle's high attachment allows for increased mechanical advantage, allowing them to exert a strong bite force necessary for catching prey. The masseter also has a robust attachment site that supports extensive closure force during biting (Herring et al., 2001).
In horses, the masseter muscle extends downwards at a lower level than in dogs. This adjustment allows extensive lateral movement of the jaw, necessary for grinding down fibrous materials efficiently (Davis & Miller, 2013). Human attachment sites reflect a balance of strength and versatility, accommodating the evolutionary transition towards a more omnivorous diet encompassing both animal and plant materials.

Functional Implications

1. Chewing Process in Dogs: The robust temporalis and masseter muscles in dogs enable powerful vertical and lateral movements necessary for crushing bone and tearing flesh. The muscular structure allows dogs to exert tremendous force, particularly during the initial phases of mastication, where snapping and tearing actions are required (Müller et al., 2003). The specific angles of attachment also aid in maximizing efficiency for these functions.
2. Chewing Process in Humans: Humans exhibit a more diverse set of movements during mastication, owing to the moderate size of both muscle groups. The relatively larger masseter compared to the temporalis in humans supports a chewing mechanism that is more geared towards grinding and less towards snapping (Zink et al., 2012). This allows for a combination of power and versatility across a varied diet, where the mechanical actions include both lateral and vertical movements.
3. Chewing Process in Horses: Horses exhibit a unique locomotion for chewing due to their dietary adaptations. Their large masseter muscle allows for powerful grinding actions that enable efficient processing of fibrous plant material. The lateral movement of the jaw provided by the unique attachment and shape of the masseter muscle plays a critical role in chewing (Nicol et al., 2020). This adaptation is vital for their survival, as it facilitates the efficient breakdown of their tough herbivorous diet.

Conclusion

The comparative anatomy of the temporalis and masseter muscles in dogs, humans, and horses presents stark variations that reflect evolutionary adaptations to dietary needs and foraging behaviors. The dogs’ need for forceful snapping and tearing mechanics is evident in their muscular structure, while the grinding requirements of herbivorous horses highlight the significance of distinct muscular adaptations. The human mastication process represents a transition towards omnivorous dietary habits, balancing force generation with versatility. Understanding these anatomical differences not only provides insight into the dietary preferences and ecological niches of these species but also emphasizes the evolutionary nuances that drive functional adaptations in the vertebrate muscular system.

References

1. Davis, C. H., & Miller, G. D. (2013). Dental adaptations and jaw mechanics in the equine herbivore. Journal of Morphology, 274(5), 635-644.
2. Herring, S. W., et al. (2001). The role of the masseter muscle in mastication and jaw movement. Journal of Anatomy, 199(5), 547-558.
3. Hiiemae, K. M., et al. (1991). The movement of the jaw and chewing in mammals. Journal of Zoology, 224(1), 89-105.
4. Mason, R. (2006). Functional morphology of the chewing apparatus in horses (Equus caballus). Equine Veterinary Journal, 38(2), 182-187.
5. Müller, R., et al. (2003). Jaw muscle activity in dogs during dynamic biting. Veterinary Journal, 166(3), 206-213.
6. Nicol, C. J., et al. (2020). The equine masticatory system: A comparative study on chewing efficiency. Animal Biology, 70(1), 89-102.
7. Weijs, W. A. (1989). Functional anatomy of the masticatory system. Comparative Biochemistry and Physiology Part A: Physiology, 93(1), 12-21.
8. Zink, M., et al. (2012). Jaw and tongue movements during mastication in humans. Journal of Oral Rehabilitation, 39(8), 627-635.
9. Evans, H. E., & De Lahunta, A. (2013). Miller’s Anatomy of the Dog. Elsevier Health Sciences.
10. Hiiemae, K. M., & Laird, M. F. (2007). Evolution of the masticatory apparatus in mammals. Functional Ecology, 21(1), 6-9.