Lab Exercise 1: Introduction to Human Anatomy
- Anatomical Position
- Surface Anatomy
- Directional Terms
- Body Planes and Regions
Anatomy is the study of body structures. This can involve study of the large parts such as muscle and organs like the heart; called gross or macroscopic anatomy or, study of structures such as what heart muscle cells look like with the aid of microscopes, microscopic anatomy. When we study what these structures do and how they do it, that is the realm of physiology. The set of exercises in Week 1 is on the organization of the human body. What are the structures on the surface of the human body, how do we name them, how do we describe their location(s) relative to each other and are we able to do these with uniformity among anatomists and physiologists? These are some of the questions we aim to be able to answer by the end of the week’s exercises.
Learning Outcomes
At the end of this lab, you should be able to
- describe the anatomical position, and explain its importance;
- use appropriate anatomical terminology to describe body regions, orientation and direction;
- recognize body planes and be able to determine whether a section is in the frontal, transverse or sagittal plane;
- name the body cavities, and indicate the important organs in each;
- name and describe the serous membranes of the ventral body cavities;
- identify the quadrants and nine regions of the abdomen on a torso model or image;
- list the 11 organ systems of the body;
- place major organs in the correct organ system when presented with a list of organs.
Anatomical position
In clinical settings and when referring to specific areas of the human body, the body is oriented in a universal position called the anatomical position. In the anatomical position (Figure 1.1), the body is upright with the feet pointed forward, eyes looking straight ahead, and arms hanging at the sides with the palms facing forward. An individual in the anatomical position is said to be prone when lying face down and supine when lying face up.
Directional Terminology
With the body in the anatomical position, specific terms are used to describe the location of a human body part relative to another (Figure 1.1a). A lateral view of an individual in anatomical position (Figure 1. 1b) illustrates the front and back orientation. Note that directional terms are with reference to the anatomical position.
(a) Lateral view (b) Anterior view
Figure 1.1. Directional Terms Applied to the Human Body Paired directional terms are shown as applied to the human body. (Credit: CNX OpenStax CC BY 4.0)
Click the link below to watch the an animation on anatomical position and directional terms:
In quadrupeds (four-legged animals), the directional terms are somewhat different.
| Table 1.1. Directional Terms Used for Humans | ||
| Term | Meaning | Example |
| Superior | Above | The mouth is superior to the chin |
| Inferior | Below | The navel is inferior to the breastbone |
| Cephalic/cranial | Toward the head | In humans, analogous to superior |
| Caudal | Toward the tail | In humans analogous to inferior |
| Anterior | To the front | The breast bone is anterior to the lungs |
| Posterior | To the back | The lungs are posterior to the breastbone |
| Medial | Toward the midline | The nose is medial to the cheek bones |
| Lateral | Away from the midline or medial plane | The kidneys are lateral to the navel |
| Ventral | Belly side | In humans, analogous to anterior |
| Dorsal | Back side | In humans, analogous to posterior |
| Superficial | Toward or at the body surface | The skin is superficial to skeleton |
| Deep | Away from the body surface | The dermis is deep to the epidermis |
| Proximal | Nearer the trunk or attached end | The elbow is proximal to the hand |
| Distal | Farther from the trunk or attached end | The fingers are distal to the wrist |
Surface and regional anatomy
The body is divided into two main regions, the axial (along the body’s main axis) and appendicular regions (the appendages and structures attaching them to the main body axis). The axial region includes the head, neck, and trunk; it runs along the vertical axis of the body. The appendicular region includes the limbs and the girdles that attach them to the trunk. These structures on the body surface constitute the body’s surface anatomy; these are shown for the anterior structures (Figure 1. 2a) and posterior structures (figure 1.2b) using the common and anatomical names. Body surface features are used as anatomical landmarks to assist in locating internal structures; as a result, many internal structures are named after an overlying surface structure.
Body Regions and Anatomical Landmarks
Figure 1.2. Regions of the Human Body The human body is shown in anatomical position in an (a) anterior view and a (b) posterior view. The regions of the body are labeled in boldface. (Credit: CNX OpenStax CC BY 4.0)
Click the link below to connect to the interactive object which enables learners to identify a person’s regional body parts.
Body Planes and Sections
To obtain different views of the internal anatomy of an organ or body cavity; sections are made along particular planes. There are THREE primary planes along which such sections can be made; two of which are vertical and one horizontal (Figure 1.3). The vertical planes are sagittal and frontal or coronal while the horizontal one is transverse. The sagittal cut or section divides the body into right and left parts; when it passes through the midline of the body, it is called midsagittal because it divides into EQUAL right and left parts. A sagittal section that divides into UNEQUAL right and left parts is called parasagittal. The frontal cut divides the body into anterior (front) and posterior (back) parts and the transverse section divides the body into superior and inferior parts.
Figure 1.3 Planes of the Body The three planes most commonly used in anatomical and medical imaging are the sagittal, frontal (or coronal), and transverse plane. (Credit: CNX OpenStax CC BY 4.0)
The body sections is narrated and illustrated in the animation; click on the link below:
Major Body Cavities
Body cavities are spaces within the body that surround internal organs. The body cavities are covered with a serous membrane that supports and protects the organs it encloses. The serous membrane has two layers one nested to the organ called the visceral layer and the outer one called the parietal layer (Figure 1.4). The space between the two layers called the serous cavity is filled with serous fluid which provides lubrication and reduces friction between the enclosed organ and adjacent organs. The body cavities of a growing child develop in the embryonic period, during the fourth to eighth week of development.
Figure 1.4 Serous Membrane Serous membrane lines the pericardial cavity and reflects back to cover the heart—much the same way that an underinflated balloon would form two layers surrounding a fist. (Credit: CNX OpenStax CC BY 4.0)
There are two major body cavities, dorsal and ventral. The dorsal cavity surrounds the brain and spinal cord.
The ventral body cavity is divided into the superior thoracic and inferior abdominopelvic cavity; each separated by the muscular diaphragm. The cavity is anterior to the vertebral column. The thoracic cavity contains the cavities surrounding the lungs, the left pleural cavity surrounding the left lung and right pleural cavity surrounding the right lung. The heart and the pericardial cavity surrounding it are located in an area between the two pleural cavities called the mediastinum. The pericardial cavity lies in the anterior part of the mediastinum. The structures in the posterior and superior parts of the mediastinum include large blood vessels esophagus and trachea.
The thoracic cavity is separated from the abdominopelvic cavity by the diaphragm. The abdominopelvic cavity consists of the superior abdominal cavity that contains most of the abdominal organs such as the liver, gall bladder, pancreas, stomach, small intestine and large intestine. The inferior pelvic cavity houses the urinary bladder internal reproductive organs parts of the large intestine including the rectum.
Figure 1.5 Dorsal and Ventral Body Cavities The ventral cavity includes the thoracic and abdominopelvic cavities and their subdivisions. The dorsal cavity includes the cranial and spinal cavities. (Credit: CNX OpenStax CC BY 4.0)
Click the link below to access this interactive learning exercise. In this interactive object, learners examine the locations of major body cavities and their protective membranes. A drag-and-drop exercise completes the activity.
Abdominopelvic Quadrants and Regions
The abdominopelvic region can be further divided into four quadrants or nine regions to provide details about the internal abdominal and pelvic organs. The vertical and horizontal planes that divide the region to four quadrants bifurcate at the navel (umbilicus) while the two vertical and two horizontal planes that divide the region into straddle the navel. In clinical practice the quadrants are used for reference while in anatomic studies the nine-region approach is often used. Identify or locate the quadrants and regions in Figure 1.6 and observe how they are named.
Figure 1.6 Regions and Quadrants of the Peritoneal Cavity There are (a) nine abdominal regions and (b) four abdominal quadrants in the peritoneal cavity. (Credit: CNX OpenStax CC BY 4.0)
Organ Systems
We have seen the structures on the body surface and how they are named; and what organs or structures are situated in particular zones or regions of the body these constitute surface and regional anatomy respectively. In systemic anatomy, the organs making up each of the ELEVEN organ systems and the functions of the systems are studied. Can you list the systems? The two systems that influence the other nine to a marked degree are the nervous system and endocrine system. The other systems include the largest organ system in terms of area covered, the integumentary system; muscular, skeletal, respiratory, cardiovascular, digestive, urinary, lymphatic and reproductive. The organ systems, some of the key organs and their functions are shown in Figure 1.7.
Figure 1.7 Organ Systems of the Human Body Organs that work together are grouped into organ systems. (Credit: CNX OpenStax CC BY 4.0)
