Anatomy and Physiology Study Guide for the HESI Exam

General Information

Anatomy and physiology are perhaps the most fundamental areas for a nurse to study. Anatomy is the area of study between biology and medicine that considers the structure of the body. Physiology is the scientific study of how the body and its organs and cells work. Understanding the location of parts of the human body is critical. A nurse must understand how each part of the body works in order to deliver the best patient outcome. For example, simply knowing where the heart is located is not enough; you must understand how the heart works and how the other systems that depend on it work in conjunction.

On the Anatomy and Physiology section of the HESI, you will find 25 questions and be allowed 25 minutes to answer them. In this study guide, we will first review some general body concepts, and the remainder of the guide will outline the systems of the body, including their structure and function.

Body Planes, Directions, and Cavities

It is important for a nurse to be able to describe locations in the body and to find the location when it is described by others. For this purpose, there are specific terms you must know.

Anatomic Position

The anatomic position is a standardized way of observing or imaging the body. In this position:

The body is upright and facing forward.
The arms are at the sides with palms facing forward.
The feet are slightly apart and pointing forward.

This position is used as a reference to describe locations and directions in medical terminology.

Body Planes

A body plane is an imaginary line that divides the body into sections. There are three major body planes:

sagittal plane (median plane)—This plane is vertical and divides the body into left and right sections. If the division is exactly in the middle, it is called the midsagittal plane. If it is off-center, it is called a parasagittal plane.
frontal plane (coronal plane)—This is the vertical plane that divides the body into anterior (front) and posterior (back) sections.
transverse plane (horizontal plane)—This is the horizontal plane that divides the body into superior (upper) and inferior (lower) sections.

1 Body Plane (1).png

Medical Imaging and Body Planes

Medical imaging techniques such as MRI and CT scans use body planes to produce detailed views of internal structures. The following scans help diagnose and monitor conditions by creating cross-sectional images of the body:

magnetic resonance imaging (MRI) scans—These can be oriented in sagittal, coronal, or transverse planes, depending on the imaging need.
sagittal MRI—This produces a side view of the body, which is useful for brain and spinal imaging.
coronal MRI—This produces a front-facing view, which is helpful in visualizing the chest and abdominal organs.
transverse MRI—This produces a top-down view, which is commonly used for brain and joint imaging.
computed tomography (CT) scans—Primarily oriented in the transverse (horizontal) plane, CT scans produce cross-sectional images from top to bottom. However, CT images can also be reconstructed in sagittal and coronal planes to provide additional perspectives. CT scans are widely used for diagnosing injuries, tumors, and internal bleeding.

Directional Terms

Directional terms describe the location of structures relative to other structures or locations in the body. These terms are essential for accurately describing body regions:

superior (cranial)—toward the head or upper part of a structure
inferior (caudal)—away from the head or toward the lower part of a structure
anterior (ventral)—toward the front of the body
posterior (dorsal)—toward the back of the body
medial—toward the midline of the body
lateral—away from the midline of the body
proximal—closer to the point of attachment or origin
distal—farther from the point of attachment or origin
superficial—closer to the surface of the body
deep—farther away from the surface of the body

These terms are often used to describe relationships between body parts, such as in describing injuries or surgical procedures.

Body Cavities

The body is divided into several cavities, which house and protect internal organs. The two major cavities are:

dorsal cavity—This is located toward the back of the body and contains two subdivisions:
- cranial cavity—houses the brain
- spinal (vertebral) cavity—houses the spinal cord
ventral cavity—This is located toward the front of the body and contains two subdivisions:
- thoracic cavity—houses the heart and lungs and includes these subdivisions:
  - pleural cavities—each surrounds a lung
  - pericardial cavity—houses the heart
- abdominopelvic cavity—contains both of these:
  - abdominal cavity—houses digestive organs such as the stomach, liver, and intestines
  - pelvic cavity—contains reproductive organs and the bladder

Each cavity is lined with membranes that provide protection and support to the organs within. The diaphragm, a muscle used for breathing, separates the thoracic cavity from the abdominopelvic cavity.

Cytology

Cytology is the study of cells, which are the basic structural and functional units of all living organisms. Cells carry out essential processes such as metabolism, growth, and reproduction. Understanding cell structure and function is fundamental to anatomy and physiology.

Cell Structure and Organelles

cell membrane (plasma membrane)—a selectively permeable barrier that regulates the passage of substances in and out of the cell
cytoplasm—the jelly-like substance that contains organelles and allows metabolic reactions to occur
nucleus—the control center of the cell that contains deoxyribonucleic acid (DNA) and regulates gene expression
mitochondria—the site of cellular respiration and adenosine triphosphate (ATP; energy) production
ribosomes—small structures responsible for protein synthesis
endoplasmic reticulum (ER):
- rough ER—studded with ribosomes; involved in protein synthesis
- smooth ER—lacks ribosomes; involved in lipid synthesis and detoxification
Golgi apparatus—modifies, packages, and distributes proteins and lipids
lysosomes—contain digestive enzymes that break down cellular waste and pathogens

Mitosis and Meiosis

Mitosis and meiosis are the two ways cells divide and reproduce. The processes are slightly different. Mitosis happens in all cells for growth and repair. Meiosis is only used by cells during sexual reproduction.

Mitosis

Mitosis is the process of cell division that allows for growth, repair, and maintenance of tissues. It produces two identical daughter cells, each with the same number of chromosomes as the parent cell. There are 46 chromosomes in humans.

Phases of Mitosis

This is what happens during each phase:

prophase—Chromosomes condense, nuclear membrane dissolves, and spindle fibers form.
metaphase—Chromosomes align at the center of the cell.
anaphase—Sister chromatids separate and move to opposite ends of the cell.
telophase—Nuclear membranes reform, chromosomes decondense.
cytokinesis—The cytoplasm divides, forming two separate cells.

Mitosis is essential for tissue repair, which includes healing wounds and replacing dead skin cells.

Meiosis

Meiosis is a specialized type of cell division that occurs only in reproductive cells (gametes). It reduces the chromosome number by half, ensuring that sperm and egg cells each carry 23 chromosomes. When fertilization occurs, the full 46-chromosome set is restored, creating genetic diversity in offspring.

Meiosis occurs in two successive stages:

meiosis I—The homologous chromosomes separate.
meiosis II—Similar to mitosis, sister chromatids separate, forming four genetically unique gametes.

This reduction in chromosome number is critical to maintaining stability in the human genome.

Histology

Histology is the study of tissues, which are groups of specialized cells that work together to perform specific functions.

Types of Tissue

The body contains the following four primary types of tissue, each serving a unique role.

Epithelial Tissue

function—protection, secretion, absorption, and filtration
location—covers body surfaces, lines cavities and organs, and forms glands
structure—can be single-layered (simple epithelium) for absorption and filtration or multi-layered (stratified epithelium) for protection in high-friction areas, such as the skin and esophagus
vascularity—avascular (lacks blood vessels); relies on diffusion from underlying connective tissues for nutrients and waste removal

Connective Tissue

function—provides structural support, connects tissues, and transports substances
location—found throughout the body, including in bones, cartilage, fat, and blood
structure—contains a matrix composed of fibers and ground substance (one key protein fiber in connective tissue is collagen, which provides strength and support)
vascularity—varies widely; bone is highly vascular, cartilage is avascular, and dense connective tissues (like tendons and ligaments) have limited blood supply, leading to slower healing times

Muscle Tissue

function—produces movement by contracting
types:
- skeletal muscle—voluntary, striated, attached to bones
- cardiac muscle—involuntary, found in the heart
- smooth muscle—involuntary, found in walls of internal organs
vascularity— highly vascular; skeletal muscles have a rich blood supply for oxygen delivery and waste removal, cardiac muscle is extremely vascular due to constant activity, and smooth muscle has moderate vascularity depending on location

Nervous Tissue

function—conducts electrical impulses for communication and coordination
location—found in the brain, spinal cord, and nerves
structure—composed of neurons, which transmit electrical signals, and neuroglia (glial cells), which provide support, protection, and nourishment to neurons
vascularity—highly vascular, especially in the brain and spinal cord, to support high metabolic activity and oxygen demands

Fluid Distribution and Interstitial Fluid

Tissues rely on the proper distribution of fluids for their function. Interstitial fluid is the fluid found in the spaces between cells within tissues. It serves as a medium for transporting nutrients, oxygen, and waste products between the blood and the cells.

Interstitial fluid originates from blood plasma, which circulates within blood vessels and delivers essential substances to tissues. Excess interstitial fluid is drained by the lymphatic system, where it becomes lymphatic fluid and is returned to circulation.

Maintaining proper fluid distribution is essential for tissue function, ensuring cells receive necessary nutrients while efficiently removing waste.

Bone Formation

Bones are a type of connective tissue that provide structure and support to the body. Osteoblasts are the specialized cells responsible for bone formation, producing the bone matrix and facilitating mineralization.