Anatomy Of A Pig Fetus

1. Place the fetal pig in a dissecting tray with its ventral side up.

Examine the nostrils (external nares) located on the the flat rostrum (snout). Open the mouth wide to expose the hard palate and the soft palate (see figs. 50.2 and 53.1). Cut through the tissues of the soft palate, and observe the nasopharynx above it. Locate the small openings of the auditory tubes in the lateral walls of the nasopharynx. Insert a probe into an opening of an auditory tube. Examine the oropharynx located near the base of the tongue. Pull the tongue posteriorly and locate the epiglottis at its base. Also identify the glottis, which is the opening into the larynx. (In the human the term glottis refers to the opening between the vocal folds within the larynx.) Locate the esophagus, which is dorsal to the larynx. Open the thoracic cavity, and expose its contents. Examine the organs located in the mediastinum. Note that the mediastinum separates the right and left lungs and pleural cavities within the thorax. Dissect the trachea in the neck, and expose the larynx at the anterior end near the base of the tongue. Note the tracheal rings, and locate the thyroid gland on the trachea, just posterior to the larynx. Locate a small parathyroid gland attached to the dorsal surface of the thyroid gland. Also note the thymus gland, extending along each side of the trachea into the thorax (fig. 53.2). Examine the larynx by removing any attached muscles, and identify the thyroid cartilage and cricoid cartilage in its wall. Make a longitudinal incision through the ventral wall of the larynx, and locate the vocal cords that appear as whitish folds inside.

Remove the heart and trace the trachea posteriorly to where it divides into bronchi, which pass into the lungs (fig. 53.3).

Examine the lungs, each of which is subdivided into lobes—a cranial, a middle, and a caudal lobe. The right lung has an additional deep acccessory lobe. Notice the thin membrane, the visceral pleura, on the surface of each lung. Also notice the parietal pleura, which forms the inner lining of the thoracic wall, and locate the spaces of the pleural cavities.

Figure 53.1 Oral cavity of the fetal pig with tongue pulled posteriorly, ventral view.

Figure 53.1 Oral cavity of the fetal pig with tongue pulled posteriorly, ventral view.

Oral Cavity Baby Pig Ventral View

Hard palate with transverse ridges

Soft palate

Nasopharynx

Esophagus

Glottis

Epiglottis

Papillae

Tissue cut at corner of mouth

Tongue

Papillae

Hard palate with transverse ridges

Soft palate

Nasopharynx

Esophagus

Glottis

Epiglottis

Papillae

Tissue cut at corner of mouth

Tongue

Papillae

10. Make an incision through a lobe of a lung, and examine its interior. Note the branches of the smaller air passages. You can see the branches of the bronchial tree if you follow a primary bronchus into the lung and gently scrape away lung tissue with a scalpel.

11. Examine the diaphragm and locate the phrenic nerve. This nerve appears as a white thread passing along the side of the heart to the diaphragm (fig. 53.2).

12. Remove a small piece of the lung and notice the solid texture of the tissue. Place the piece of lung into a beaker of water. Does the fetal lung tissue float or sink?_

13. Complete Laboratory Report 53.

Critical Thinking Application

Under what conditions would a piece of lung tissue sink?

Critical Thinking Application

Under what conditions would a piece of lung tissue sink?

Under what conditions would it float?

Figure 53.2 Respiratory organs and glands of the fetal pig, ventral view.

Larynx Thymus gland

Right common carotid artery

Right atrium

Right lung

Right phrenic nerve Posterior vena cava

Figure 53.2 Respiratory organs and glands of the fetal pig, ventral view.

Larynx Thymus gland

Right common carotid artery

Right atrium

Right lung

Right phrenic nerve Posterior vena cava

Thyroid Cartilage Fetal Pig

Thyroid cartilage

Cricoid cartilage Trachea

Parathyroid gland Thyroid gland

Thymus gland

Left atrium

Left ventricle

- Left lung

Left phrenic nerve Diaphragm

Thyroid cartilage

Cricoid cartilage Trachea

Parathyroid gland Thyroid gland

Thymus gland

Left atrium

Left ventricle

- Left lung

Left phrenic nerve Diaphragm

Phrenic Artery Diaphragm Muscle
Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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