Human Skeletal System

Comprises 206 bones that provide support, protection, and movement for the body
Divided into two main parts:
- Axial skeleton: skull, vertebral column, ribs, and sternum
- Appendicular skeleton: upper and lower limbs, pelvis, and shoulder girdle
Functions:
- Support: provides framework for the body
- Protection: protects internal organs
- Movement: acts as a system of levers and joints to facilitate movement
- Blood cell production: bones are responsible for producing blood cells
- Storage: stores minerals such as calcium and phosphorus

Consists of two main parts:
- Central nervous system (CNS): brain and spinal cord
- Peripheral nervous system (PNS): nerves that connect the CNS to the rest of the body
Functions:
- Control: regulates and coordinates body functions
- Communication: transmits and receives information
- Integration: interprets and responds to sensory information
- Movement: controls voluntary and involuntary movements
Types of nerves:
- Motor nerves: transmit signals from CNS to muscles and glands
- Sensory nerves: transmit signals from sensory receptors to CNS
- Mixed nerves: contain both motor and sensory fibers

Comprises:
- Upper respiratory tract: nose, mouth, pharynx, and larynx
- Lower respiratory tract: trachea, bronchi, bronchioles, and lungs
Functions:
- Gas exchange: takes in oxygen and removes carbon dioxide
- Filtration: filters out dust, bacteria, and other particles
- Regulation: regulates pH levels by removing excess hydrogen ions
Mechanisms:
- Inspiration: diaphragm and intercostal muscles contract to expand chest cavity
- Expiration: diaphragm and intercostal muscles relax to decrease chest cavity

Comprises:
- Lymphatic vessels: network of vessels that transport lymph
- Lymph nodes: filters that remove pathogens and debris from lymph
- Lymphoid organs: spleen, thymus, and lymphoid tissues
Functions:
- Defense: protects against infection and disease
- Drainage: returns proteins and excess fluids to the bloodstream
- Fat absorption: absorbs fats and fat-soluble vitamins from the digestive system
Mechanisms:
- Lymphatic circulation: lymph flows through vessels and nodes to filter out pathogens
- Immune response: activates immune cells to fight infection

Comprises:
- Innate immunity: non-specific defense mechanisms
- Adaptive immunity: specific defense mechanisms that recognize and respond to pathogens
Functions:
- Defense: protects against infection and disease
- Recognition: recognizes and responds to specific pathogens
- Memory: retains memory of pathogens for future immunity
Mechanisms:
- Activation: immune cells are activated to respond to pathogens
- Response: immune cells respond to pathogens through inflammation, antibody production, and cell-mediated immunity
- Regulation: immune response is regulated to prevent overreaction and autoimmune disease

The skeletal system provides support, protection, and movement for the body through 206 bones
Axial skeleton consists of skull, vertebral column, ribs, and sternum
Appendicular skeleton comprises upper and lower limbs, pelvis, and shoulder girdle
Bones function as a system of levers and joints to facilitate movement
Bones are responsible for producing blood cells
Minerals like calcium and phosphorus are stored in bones

The central nervous system (CNS) consists of the brain and spinal cord
The peripheral nervous system (PNS) consists of nerves connecting the CNS to the rest of the body
The nervous system regulates and coordinates body functions
It transmits and receives information through nerve impulses
It interprets and responds to sensory information
Motor nerves transmit signals from CNS to muscles and glands
Sensory nerves transmit signals from sensory receptors to CNS
Mixed nerves contain both motor and sensory fibers

The upper respiratory tract consists of nose, mouth, pharynx, and larynx
The lower respiratory tract consists of trachea, bronchi, bronchioles, and lungs
The respiratory system takes in oxygen and removes carbon dioxide through gas exchange
It filters out dust, bacteria, and other particles through the filtration mechanism
It regulates pH levels by removing excess hydrogen ions
Inspiration occurs when the diaphragm and intercostal muscles contract to expand the chest cavity
Expiration occurs when the diaphragm and intercostal muscles relax to decrease the chest cavity

The lymphatic system consists of lymphatic vessels, lymph nodes, and lymphoid organs
Lymphatic vessels transport lymph throughout the body
Lymph nodes filter out pathogens and debris from lymph
Lymphoid organs, such as the spleen and thymus, are responsible for immune function
The lymphatic system protects against infection and disease through defense mechanisms
It returns proteins and excess fluids to the bloodstream through drainage
It absorbs fats and fat-soluble vitamins from the digestive system
Lymphatic circulation involves the flow of lymph through vessels and nodes to filter out pathogens
The immune response is activated to fight infection

The immunologic system consists of innate immunity and adaptive immunity
Innate immunity provides non-specific defense mechanisms against infection
Adaptive immunity provides specific defense mechanisms that recognize and respond to pathogens
The immunologic system protects against infection and disease through defense mechanisms
It recognizes and responds to specific pathogens through recognition mechanisms
It retains memory of pathogens for future immunity
Immune cells are activated to respond to pathogens through activation mechanisms
The immune response is regulated to prevent overreaction and autoimmune disease