Understanding How Structure Determines Function (2025)

Objectives

1. Introduce students to the study of the human body.
2. Define and illustrate the anatomical position.
3. Define directional terms and apply directional terms to descriptions of the human body.
4. Define and describe anatomical planes by section.
5. Locate and describe the divisions of major human and the serous membrane covering them.
6. Identify the organ systems of the human body, their functions, components, and interactions.

Levels of Organization

The human body can be studied from a number of perspectives, mainly, gross anatomy and microscopic anatomy. In this section, we will focus on gross anatomy, but we need to consider the levels of organization of the human body, starting with chemical, organelle, cellular, tissue, organ, organ system, and organisms.

Anatomical Position

The anatomical position allows health care providers to communicate consistently giving the proper orientation when dealing with patients.

The anatomical position refers to upright, facing forward, arms and legs straight, palms facing forward, feet flat on the ground, and eyes open.

With the body in anatomical positions, there are specific terms to describe parts of the body with respect to each other.

Table No. 1 – Directional terms

Planes of sectioning

Planes of sectioning are cuts that divide the body into sections.

Sections

Horizontal or transverse plane: separate the body into superior and inferior parts.

Frontal or coronal: separate the body into anterior-posterior

Sagittal: separate the body into right and left portions

Midsagittal: separate the body into equal right and left portions

Parasagittal: separate the body into unequal right and left portions.

Sectional Planes of the Brain

Body Cavities & Serous Membranes

A cavity is an enclosed space inside the body. The human body is divided into two major cavities; ventral (anterior) and dorsal (posterior) and each cavity is subdivided into smaller cavities. They are fluid-filled and contain specific organs. Several of the fluid-filled cavities are formed by thin sheets of tissue, named serous membranes, the cells that form these membranes produce a watery fluid that resembles the serum, that fluid is called serous fluid that lubricates and protects the organs inside those cavities. The serous membranes are composed of two layers, parietal (attached to the body wall) and visceral (attached to specific organs).

The posterior cavity is divided into two smaller cavities; Cranial and Vertebral cavities.

• The Cranial cavity is the area encased by the skull, contains the brain and it is filled with cerebrospinal fluid.
• The vertebral cavity is the area encased by the vertebral column (stacked vertebrae), contains the spinal cord and it is filled with cerebrospinal fluid.

The anterior cavity has two main divisions; the thoracic and abdominopelvic cavities, they are separated by a muscle, the diaphragm. The thoracic cavity is located superior to the diaphragm, it is subdivided into the pleural cavities and the mediastinum.

• The pleural cavities, each pleural cavity surrounds on of the lungs. They are located between two layers of serous membrane, the pleural membrane. These layers are called the parietal pleura (attached to the body wall and the diaphragm) and the visceral pleura (attached to the lungs), between the two there is a thin layer of pleural fluid.

The Abdominopelvic cavity is located inferior to the diaphragm. There are three sub-cavities:

• Abdominal cavity – houses many organs; liver, gallbladder, small intestine, stomach, pancreas, kidneys, adrenal glands, spleen and a portion of the large intestine
• Pelvic cavity – contains sex organs, urinary bladder, rectum and part of the colon.

Peritoneal cavity – formed by serous membranes called the peritoneum. The peritoneum is formed by two layers, the outer layer, the parietal peritoneum that is attached to the body wall and the visceral peritoneum that is attached to many organs of the abdominal and pelvic cavities. Only the organs that are within the peritoneal cavity are called intraperitoneal, the rest are referred as retroperitoneal.

Body Cavities and Membranes (Dorsal, Ventral)- Anatomy and Physiology

Body Cavities – Drawn & Defined

Body Cavities and serous membranes

Regions of the Body

Anatomical regions refer to terms used for specific parts of the body.

These terms include:

Abdominal Regions

The abdomen can be further divided into four quadrants or nine regions. These are very important in clinical practice.

Four quadrants

Nine Regions

These regions are shown in the figure below.

Organs in the Abdominal Regions

Subdivisions of the Abdomen

Organ Systems

The human body consists of several organ systems that work together to maintain homeostasis. The study of organ systems is also referred to as Systemic Anatomy.

Even though we will study the 10 major organ systems of the body separately, there is no real separation; they in fact work all together via close connections, interactions, and chemical signals.

In this lab, we will introduce the organ systems and its components:

• The integumentary system – provides a protective covering to the body
• The muscular system – provide movement to the body
• The skeletal system – provides framework for movement and protection of the organs of the body
• The nervous system – allows us to interact and interpret the environment (inside and outside)
• The endocrine system – produce hormones
• The cardiovascular system (circulatory and lymphatic system)
• Circulatory system – to transport substances in the body
• Lymphatic system – cleanses and returns tissue fluid to the circulatory system
• The respiratory system – exchange of oxygen for carbon dioxide
• The digestive system –to provide nutrition (fuel) to the tissues of the body
• The urinary/excretory system – discard body waste products
• The reproductive system – responsible for maintenance of species

The Integumentary System

The integumentary system consists of the covering of the body (the skin), including hair and nails as well as other functionally important structures such as the sweat glands and sebaceous glands. The skin is the largest organ we have, it forms a boundary between our delicate inside and the harsh outside environment. It provides containment, structure, and protection for other organs, but it also serves as a major sensory interface with the outside world.

The Musculoskeletal System

The musculoskeletal system consists of the human skeleton (which includes bones, ligaments, tendons, and cartilage) and attached muscles. It gives the body basic structure, protection to important organs, and the ability for movement. In addition to their structural role, the larger bones in the body contain bone marrow, the site of production of blood cells. Also, all bones are major storage sites for calcium and phosphate. This system can be split up into the muscular system, the skeletal system and joints and articulations.

Video – Joints

Ankle joint

Elbow joint

Video – Muscles

Gluteal Muscles

Erector spinae

The Nervous System

The nervous system consists of the central nervous system (CNS; brain and spinal cord) and the peripheral nervous system (PNS; consist of nerves and ganglia outside the CNS. Includes cranial and peripheral nerves, except cranial nerve II). The brain is the control center of the body. It is the organ of thought, emotion, memory, and sensory processing. It allows for communication and controls of various organ systems in the body. The brain is basically divided in three regions; forebrain, midbrain and hindbrain. The nervous system also includes our special senses; vision, hearing, taste, smell and touch. The eyes, ears, tongue, and nose gather information about the body’s environment.

Videos

Hypoglossal nerve

Visual Pathways

Anatomy of the brain – dissectible model

The Endocrine System

The endocrine system consists of the principal endocrine glands: the pituitary (anterior and posterior), thyroid, parathyroid, pancreas, adrenals, and gonads Ovaries and testes), but nearly all organs and tissues produce specific endocrine hormones as well. The endocrine hormones serve as signals from one body system to another regarding an enormous array of conditions and resulting in variety of changes of function. There is also the exocrine system.

The Endocrine System

Cardiovascular System

The cardiovascular system delivers oxygen and nutrients to tissues and equalizes temperature in the body.

Video link – Cardiovascular anatomy introduction

The human circulatory system (simplified). Red indicates oxygenated blood, blue indicates deoxygenated.

Video – Carotid body and carotid sinus anatomy

Lymphatic System

The lymphatic system is part of the circulatory system. It consists of lymphatic organs, lymphatic tissue, lymphatic vessels and lymph. The main function of the lymphatic system is to assist the circulatory system in transporting lymph (the fluid found in between cells Interstitial fluid). The lymphatic organs include the thymus, spleen, lymph nodes, and tonsils. Lymphatic tissue includes Peyer’s patches (small intestine). The lymphatic vessels include right duct, thoracic duct, cisternae chili and lymph vessels. Lymph is very similar to blood plasma, contains white blood cells, waste products, debris of cells, bacteria and proteins.

The Immune System

The immune system consists of the white blood cells, the thymus, lymph nodes and lymph channels, which are also part of the lymphatic system. The immune system provides a mechanism for the body to distinguish its own cells and tissues from alien cells and substances and to neutralize or destroy the latter by using specialized proteins such as antibodies, cytokines, and toll-like receptors, among many others.

The Respiratory System

Respiratory System

• Removes carbon dioxide from the body
• Delivers oxygen to blood

The respiratory system consists of the nostrils, nose, nasal cavity, nasopharynx, trachea, bronchi, bronchioles and lungs. The lungs serve as a site for exchange of gasses, carbon dioxide from metabolic waste from cells with oxygen from the air. The respiratory system also has a minor function as an excretory organ.

The Digestive System

The digestive system processes food for use by the body and removes waste from undigested food.

The digestive system consists of the mouth including the tongue and teeth, esophagus, stomach, gut (gastrointestinal tract (GI), small and large intestines, and rectum). It also has accessory organs such as the liver, gallbladder, pancreas, and salivary glands. It converts the food we ingest into smaller units of nutritional content, to be absorbed by the intestines into circulation for further distribution of fuels for all cells of the body. The circulatory system absorbs what is needed, and excretes the unused residue as feces.

Video – stomach

The Urinary System

The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. It removes metabolic wastes from the blood to produce urine, which carries a variety of waste molecules and excess ions and water out of the body. The kidneys are the major organs of filtration; they consist of millions of functional units called nephrons. The nephrons are composed of the renal corpuscle (glomerulus and Bowman’s capsule) and the tubules (proximal convoluted tubule, loop of Henle, distal convoluted tubule). The collecting ducts collect urine from several nephrons and drain into the minor calices.

Video – Kidney Anatomy

The Reproductive System

The reproductive system consists of the gonads and the internal and external sex organs. The reproductive system produces gametes in each sex (sperm and oocytes), a site for their combination (fertilization) and formation of the zygote, implantation of the zygote and a nurturing environment for the first 9 months of development of the fetus into an infant.

Video – Inguinal Canal

Laboratory Activity

Activity A – Regional Terms

1. Use the images of the Mini Muscle Man/Woman (anterior and posterior view) to label the regions shown.

2. Find the following locations of the body using the muscle man image (above), then provide the appropriate regional terms on the table shown below

Activity B – Relative Positions, Planes and Sections

You will use a green or hard yellow banana, a green onion, a plastic knife and black sharpie.

Procedure

1. Review the following terms:
   1. Longitudinal
   2. Coronal
   3. Sagittal
   4. Parasagittal
   5. Horizontal
   6. Transverse
2. Do not peel your banana.
3. Using the caricature shown here as an example, mark the following regions on your banana peel
   1. Anterior
   2. Posterior
   3. Cephalic (superior)
   4. Caudal (inferior)
   5. Right and Left
4. Take a picture of your banana to upload on your Learning Management System (LMS).
5. Perform the following cuts:
   
   What type of section is this?
   
   What type of section is this?
   
   What type of section is this?
6. Also perform the following cuts:
   1. Sagittal
   2. Coronal
   3. Transverse
   4. Parasagittal
7. Mention two types of longitudinal cuts:
   
8. Is a transverse cut the same as a horizontal cut? And a cross section (c.s.)?
   
9. Using a green onion, perform a transverse cut, oblique cut and a longitudinal cut.
   

What do you see, how does this related to a cut through a section of small intestine?

What type of sections is shown here?

Activity C – Identify Planes and Sections

1. These are images of the brain. Name the type of section performed in each of the images shown below:

For 100% online courses, skip using the brain images and use the drag and drop activity provided below to complete the labeling activities.

Activity D – Body Cavities

1. Name the body cavities shown on these images – use the table provided below.

Activity E – Label the regions of the abdomen

1. Label the 4 quadrants of the abdominal area
   
2. Name the organs located in the epigastric region
   
3. Name the organs located in the right iliac region
   
4. Name the organs located in the left lumbar region

Activity 4 – Organ systems

1. Label the name of the organ and by the side of the name in parenthesis write the name of the organ system to which that organs belongs to.
   
2. Locate and label the following organs on the torso model’s images shown here in the tables
   

   Organ	Organ System
   Brain
   Spinal Cord
   Thyroid gland
   Adrenal glands
   Pancreas
   Ovaries
   Testis
   Heart
   Larynx
   Lungs
   Trachea
   Esophagus
   Stomach
   Small intestine
   Large intestine
   Vermiform Appendix
   Rectum
   Liver
   Gallbladder
   Spleen
   Axillary Lymph nodes
   Urinary bladder
   Ureters
   kidneys
   Prostate gland
   Urethra
   Mammary glands
   Abdominal Aorta
   Superior Vena Cava
   Inferior Vena Cava

3. Name the components of the Endocrine system
   

4. Name the components of the male urinary system

Activity 5 – Critical thinking/Apply what you learned today

1. Describe using anatomical and directional terms the location of the tattoo shown here

Plastic Anatomy – By Sam Webster

Feel free to review the following short videos and animations to complement your lab:

Thorax organs – plastic anatomy

Blood supply to small intestine

Abdominal organs

Arcuate line

Ureters

Blood supply to the stomach

Hepatic Portal vein

Aorta

Stomach

Gall bladder and biliary tree

Spleen anatomy

Pancreas anatomy

Liver anatomy

Large intestine anatomy

Small intestine anatomy

Inguinal canal

Posterior Abdominal wall

Adrenal glands

Kidney anatomy

Peritoneum in cling film

Vena Cava

The greater omentum

The lesser omentum

Round ligament of liver or ligamentum teres

Vagus nerve anatomy

Cardiovascular anatomy

Duodenum

Abdomen transverse CT imaging anatomy

Heart Anatomy

Female pelvic organs introduction

The Urinary System

• Label the main structures of the Urinary System. After completing this activity, self-assess your answers by comparing with the key provided in the next page.

For 100% online courses, skip using the brain images and use the drag and drop activity provided below to complete the labeling activities.

The Skeletal System – Diagrams

Label the main bones of the human body.

The Respiratory System

The human respiratory system is divided into the upper and lower tracts. The upper respiratory tract includes the nose and nasal passages, paranasal sinuses, the pharynx, and the portion of the larynx above the vocal folds (cords). The lower respiratory tract includes the portion of the larynx below the vocal folds, trachea, bronchi, and bronchioles. The lungs are included in the lower respiratory tract.

Activity

• Label the main structures of the Respiratory System. After completing this activity, self-assess your answers by comparing with the key provided in the next page.

For 100% online courses, skip using the brain images and use the drag and drop activity provided below to complete the labeling activities.

The Reproductive System

Label the diagrams

• Female – sagittal section of pelvis
  

• Male – sagittal section of pelvis
  

The Muscular System

Review the main muscles of the human body

File: Muscles anterior labeled.png https://commons.wikimedia.org/wiki/File:Muscles_anterior_labeled.png This work is in the public domain in its country of origin and other countries and areas where the copyright term is the author’s life plus 100 years or fewer.

File: Muscle posterior labeled.png https://commons.wikimedia.org/wiki/File:Muscle_posterior_labeled.png This work is in the public domain in its country of origin and other countries and areas where the copyright term is the author’s life plus 100 years or fewer.

The Integumentary System

Label the diagram – components of the integumentary system

Hair

Nail

Skin

Glands in skin

The Endocrine System

• Label the main structures of the Endocrine System. After completing this activity, self-assess your answers by comparing with the key provided in the next page.
  

For 100% online courses, skip using the brain images and use the drag and drop activity provided below to complete the labeling activities.

The Digestive System

The gastrointestinal tract, also called the digestive tract, alimentary canal, or gut, is the system of organs within multicellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste.

Label the main structures of the Digestive System. After completing this activity, self-assess your answers by comparing with the key provided in the last page.

For 100% online courses, skip using the brain images and use the drag and drop activity provided below to complete the labeling activities.

The Nervous System

Label the components of the CNS: Brain and Spinal cord.

The Cardiovascular System

The cardiovascular system includes the heart, blood vessels, and blood which is located inside the blood vessels and circulates throughout the entire body bringing nutrients to all cells and removing their metabolic waste.

Label the main structures of the Cardiovascular System.