Introduction to Anatomy & Physiology
Human anatomy and physiology is the study of the structures and functions of the human body. This section will uncover common structures that are vital to each of the body’s systems and explain how many of these structures work together to influence each system to function as a complete body system.
The body can be studied at seven structural levels: chemical, organelle, cell, tissue, organ, organ system, and organism. At the organismal level, the human body can be divided in multiple ways, with directional terms that refer to the body being in the anatomical position. The human body also has multiple body cavities and four primary tissues: connective, epithelial, muscular, and nervous. The body’s subsequent levels of organization all work together to maintain homeostasis, a relatively constant environment within the body.
| Body System | Organ Structures | Functions |
|---|---|---|
| Skeletal System | Bones, cartilage, and ligaments | Support bodily movement and coordination, protect vital organs |
| Muscular System | Cardiac, skeletal, and smooth muscle | Bodily movement, support, stabilizing joints, and generating body heat |
| Nervous System | Brain and spinal cord | Coordinates bodily responses by interpreting internal and external stimuli; governs consciousness, learning ability and personality |
| Cardiovascular System | Blood, heart, and blood vessels (arteries, veins, and capillaries) | Transport oxygen rich blood to the body and carry carbon dioxide to the lungs for elimination via exhalation |
| Respiratory System | Nose, nasal cavity, mouth, larynx, pharynx, trachea, lungs, and diaphragm | Brings oxygen into the body in exchange for carbon dioxide |
| Digestive or Gastrointestinal | Mouth, pharynx, esophagus, stomach, intestines | Break down food for nutrient absorption and eliminate waste |
| Integumentary System | Skin, hair, nails, sebaceous and sweat glands | Protect the body and provide sensory information from external stimuli |
| Lymphatic or Immune System | Spleen, tonsils, adenoids, appendix, thymus gland, and lymph nodes | Provides immunity against pathogens and fights infection |
| Urinary or Renal System | Kidneys, ureters, bladder, and urethra | Regulates water and salt concentration in the blood, eliminates waste, and secretes hormones |
| Endocrine System | Hypothalamus, pituitary gland, thyroid gland, pineal gland, adrenal glands, thymus, pancreas, ovaries or testes | Uses hormones and chemical signals to maintain bodily functions |
| Reproductive System | Male: penis, testicles, and sperm Female: uterus, ovaries, and ova | Internal fertilization within the female reproductive system and delivery of an infant |
Skeletal System Overview
- The skeletal system provides structural support and protection, aids in movement, serves as a mineral reservoir, and helps produce cells.
- A human is born with roughly 270 bones. As a person grows, this number decreases to approximately 206. This is because many of the bones fuse.
- The appendicular skeleton consists of the upper and lower extremities.
- The axial skeleton consists of the skull, sternum, ribcage, and vertebral column.
- The five bone types in the human body are: long, short, flat, irregular, and sesamoid.
- Joints are the places where bone connects to bone to allow for a range of movement. There are six types of joints in the body.
- Ossification is a bone-forming process typically performed in childhood.
- Bone remodeling is a process that involves replacing old, mature bone tissue with new bone.
Anatomy of the Muscle
- There are over 600 muscles in the body. Muscles are grouped according to characteristics such as size, shape, and location.
- Tendons attach muscle to bone and help bones move.
- Cardiac, smooth, and skeletal muscles are the three muscle types found in the body.
- Cardiac muscle is found in the walls of the heart and smooth muscle is found in the walls of internal organs. These muscle types are under involuntary control.
- Skeletal muscles move bones by working in muscle pairs to contract and elongate. Skeletal muscle is under voluntary control.
- Three types of muscle tissues comprise a skeletal muscle: epimysium, endomysium, and perimysium.
What Is the Nervous System?
- The nervous system performs sensory, integrative, and motor functions.
- The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS).
- The somatic nervous system controls voluntary activities, while the autonomic nervous system is responsible for involuntary activities under unconscious control.
- The sympathetic nervous system focuses on emergency “fight or flight” situations, while the parasympathetic nervous system controls involuntary processes dealing with “rest or digest” activities.
- The three major regions of the brain are the cerebrum, brainstem, and cerebellum.
- The limbic system consists of the hypothalamus, thalamus, hippocampus, and amygdala, each of which has different purposes related to processing information, generating responses, and memory.
- Four lobes comprise the cerebral cortex, which is grey matter that surrounds the cerebrum.
- White matter is found in the spinal cord and surrounds grey matter. Grey matter is also known as the cerebral cortex, which is comprised of four lobes that surrounds the cerebrum and contains interneurons.
- Neurons are the specialized nerve cells which send and receive messages throughout the body. Neurons can be sensory, integrative, or motor.
- Neurons are made of dendrites, a cell body, an axon, and an axon terminal.
- A neuron must be excited from a stimulus to create a nerve impulse and send messages by way of neurotransmitters, or chemical messengers.
- Myelin sheath insulates the axon of neuron, increasing the spread of electric signal transmission.
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