Chapter 1 Bio 201

Section 1.2 Anatomy Terminology & Organ Systems

Anatomical Position

• Anatomical Position is a position in which:

  •  the body is erect

  • feet slightly apart (shoulder width)

  • palms facing forward (anterior/ventral)

  • thumbs pointing away (laterally) from the body

• An understanding of anatomical position is crucial since it provides a universal frame of reference regardless of the body’s actual position. 

• Keep in mind, the directional terms that follow, will always refer to the body in its anatomical position. 

Directional Terms

One of the most daunting tasks for students to overcome in their first anatomy & physiology course is the terminology. Much like learning a new language, the key to success in this course is repetition & being able to integrate the new terms into your everyday vocabulary. Let’s begin our journey into the terminology by becoming familiar with the directional terms. 

• Anterior: (aka ventral) means toward the front of the body.

• Posterior: (aka dorsal) means toward the back/rear of the body.

• Superior: means toward the head or upper portion of the body.

• Inferior: means toward the tail or lower portion of the body or away from the head or upper portion of the body.

• Medial: means towards the midline or center of the body only. Not to be confused with the term median.

• Lateral: means away from the midline or center of the body.

• Median: means towards the midline or the center of the body or any body part or section that has left & right halves.

• Superficial: means toward the surface of the body or skin.

• Deep: means away from the surface or toward the body’s interior, as close to the bones, cartilages, or organs. 

• Intermediate: means its in-between the superficial & deep layers. 

The 2 directional terms listed below are used especially in the anatomy of the limbs:

• Proximal: means toward the point of origin or something relatively close to the limb's point of attachment, such as the the shoulder, elbow, arm, wrist, hip, leg, knee, or ankle.

• Distal: means away from the point of origin or something farther away from the limb's point of attachment.

Lastly, these last 2 directional terms you need to know might seem easy. But it does become challenging when you don't orient yourselves properly. Knowing left from right & vise-versa is an important safety factor to always consider in the medical field. Mislabeling left from right & vise-versa can have severe medical or legal consequences in the medical field, such as injuries or even death. 

• Note: Every time we are asking you to state whether a structure or body part is in its left or right side, always refer back the cadaver, plastic model, specimen, or image's left or right sides in the anatomical position. 

Figure 1.7 Directional Terms

Regional Terms

Regional terms are used in anatomy & physiology in order to make descriptions as specific as possible. 

• For instance, if someone were to say that they had a deep cut in their chest, it would not be very clear as to where exactly the cut was located. However, if someone were to say they had deep cut in their sternal region, you would have a much better understanding of where the cut was located.

• These are new terms that you've never imagine of using or understanding. But remember, in the context of anatomy & physiology, even in the medical field, these terms are utilized & verbalized on a regular basis, so use this opportunity to learn, add, & use them in your vocabulary in a medical setting.

• Become familiar with the regional terms shown & listed below. 

• Note: Moving forward, you must include the word region in your answer for it to be considered a complete answer. 

Figure 1.8 Regional Terms

Table 1.1 Regional Terms

Serous Membranes & Body Cavities

Internally, the human body is organized into spaces known as body cavities. But before we discuss the body cavities, let's talk about serous membranes first:

• Many of these body cavities house specific organs. They are fluid filled & lined with thin layers of tissue known as serous membranes (not serious). 

• Serous Membranes: 

  • These thin layers of tissue are composed of 2 layers & cells that produce a thin watery substance known as serous fluid. 

    • 2 Layers: 

      • An outer parietal layer (some examples: parietal pericardium & parietal pleura).

        • This layer is attached to the body wall & its structures.

      • An inner visceral layer (some examples: visceral pericardium & visceral pleura).

        • This layer is attached to specific internal organs, also known as viscera (singular: viscus not viscous). 

    • Serous fluid: 

      • Serves as a lubricant for the organs allowing them to move freely without friction within the cavity (some examples: pleural fluid & pericardial fluid). 

      • It is found in the space between the parietal & visceral layer (some examples: pleural space & pericardial space). 

The body is enclosed between 2 major cavities: anterior & posterior cavities:

Major Cavity 1 - Anterior/Ventral Cavity: Made up of 2 minor cavities: thoracic & abdominopelvic cavities, which contains organs/structures found in the anterior side of the body. The cavities are separated by a thin muscle called the diaphragm.

• Minor Cavity 1 - Thoracic Cavity: A cavity located above the diaphragm & encases the organs/structures found in the chest only. Made up of 3 smaller cavities: mediastinum, pleural, & pericardial cavities.

  • Mediastinum: A space between the lungs, that starts from the base of the neck to the diaphragm. 

    • It contains the heart, esophagus, great blood vessels, trachea, bronchi, lymph nodes, lymph vessels, & some important nerves. 

  • Pleural Cavity: (not plural) Spaces that surround each lung. 

    • It contains the serous membranes called the parietal & visceral pleura.

    • It also contains the serous fluid called pleural fluid.

  • Pericardial Cavity: A space between the lungs that contain the heart & other cardiac structures only.

    • It contains the serous membranes called the parietal & visceral pericardium.

    • It also contains the serous fluid called pericardial fluid.

    • "Peri-" means around

    • Note: The heart is found both in the mediastinum & pericardial cavity. Pay attention to the inclusion of the word "only" in the question. 

• Minor Cavity 2 - Abdominopelvic Cavity: The space found below the diaphragm, that contains majority of the digestive, urinary, lymphatic, endocrine, & reproductive organs. Made up of 3 smaller cavities: abdominal, peritoneal, & pelvic cavities.

  • Abdominal Cavity: A space located above the pelvic cavity. It spans from the diaphragm to the the pelvic brim. Contains most of the digestive organs & some urinary, endocrine, & lymphatic organs. Inside this cavity is minor cavity 2, which will hold & suspend the organs in place, otherwise all those organs will pile up at the bottom of the cavity.

  • Peritoneal Cavity: A space found between the 2-layered serous membrane called the peritoneum. 

    • The 2 layers of the peritoneum are called the:

      • Outer parietal peritoneum: lines the wall of the cavity. When the posterior midline part of this layer, turns inward it then becomes the visceral peritoneum.

      • Inner visceral peritoneum: suspends certain abdominal viscera form the body wall, covering their outer surfaces & holding them in place.

    • It also contains the serous fluid called peritoneal fluid.

    • Intraperitoneal: Organs that are within the peritoneal cavity,which include the liver, most of the small intestine, much of the colon, the stomach, the spleen, & part of the pancreas. 

    • Retroperitoneal

      : Those organs that are posterior to the peritoneal cavity & its other side lie against the posterior body wall, include the kidneys, adrenal glands, the sex organs, the urinary bladder, part of the colon, & part of the pancreas.

  • Pelvic Cavity: Located below the pelvic brim. Contains some organs of the urinary, digestive, & reproductive systems; such as the urinary bladder, ovaries, rectum, & prostate gland.

Major Cavity 2 - Posterior/Dorsal Cavity: Made up of 2 minor cavities: cranial & vertebral cavities, which pretty much contains the major organs of the nervous system.

• Minor Cavity 1 - Cranial Cavity: Contains the brain, enclosed in the skull.

• Minor Cavity 2 - Vertebral Cavity: Contains the spinal cord, enclosed in the vertebrae.

• Note: Both cavities are lined with membranes called meninges (singular: meninx), instead of serous membranes.  

Figure 1.9 Body Cavities

Quadrants

The abdominopelvic cavity can be divided into 4 quadrants or 9 regions. For the purposes of this course, we will focus on the 4 quadrants: right upper, right lower, left upper & left lower. Take note of the organs that can be found within each quadrant. Some organs or parts of an organ may be found in multiple quadrants. Recognize that not all organs can be seen in the image since they may be located deep to the organs in the picture. If you've never heard of these organs before, then this is the time to familiarize yourselves with them.

Figure 1.10 Body Quadrants

Planes & Sections

Often times, it is necessary to obtain different views of organs or specific body cavities. 

• A plane is an imaginary flat surface that passes through the body or its organs. 

  • The sagittal plane divides the body or organs into left & right parts. 

    • A midsagittal plane is when the body or its organs are divided into equal left & right parts. 

    • A parasagittal plane divides the body or its organs into unequal left & right parts. 

    • Note: there is only 1 midsagittal plane, but many parasagittal planes. 

    • Pay close attention to the correct spelling of the term sagittal, which has 2 T's, 1 G, & 1 L. 

  • A frontal/coronal plane divides the body or its organs into anterior/ventral & posterior/dorsal parts. 

  • A transverse/cross section/horizontal plane divides the body or its organs into superior (or proximal) & inferior (or distal) parts. 

• A section is a cut or slice taken to view the internal anatomy. Shown on figure 1.12

Figure 1.11 Body Planes

Figure 1.12 Body Sections in an MRI Imaging: A) Sagittal, specifically the Right Midsagittal section; B) Coronal Section; C) Transverse Section

Organ Systems

The human body has 11 organ systems with specific functions & organs associated with them. It is important to recognize the different organ systems, but understand that they all work together to sustain life. The table below provides a brief summary of the principal functions & organs associated with each system. 

Figure 1.13 Organ Systems

Table 1.2: Summary of the 11 Organ Systems, their function, & the organs found in each system

Identifying Organs

 Identify the following organs on your preserved mammal specimen or human torso models. Check off each organ as you identify it, and record the organ system to which it belongs in Table 1.3, using Figure 1.13 for reference. Remember that some organs may function in more than one system.

•  Adrenal glands

•  Blood vessels

•  Bones 

• Brain 

• Esophagus 

• Gallbladder 

• Heart 

• Joints 

• Kidneys 

• Large intestine 

• Larynx 

• Liver 

• Lungs 

• Lymph nodes 

• Pancreas

• Skeletal muscles 

• Skin 

• Small intestine 

• Spinal cord

• Spleen

• Stomach

• Testes (male) or ovaries (female) 

• Thymus

• Thyroid gland 

• Trachea 

• Urinary bladder 

• Uterus