⭐ Organ systems

What does the mnemonic “MURDERS LINC” stand for?

M – Muscular; U – Urinary; R – Respiratory; D – Digestive; E – Endocrine; R – Reproductive; S – Skeletal; L – Lymphatic; I – Integumentary; N – Nervous; C – Cardiovascular.

What structures make up the integumentary system?

Skin, Hair, Nails, Glands, Connective tissue, Small muscles in skin.

What are the main functions of the integumentary system?

Prevents water (H₂O) loss, Prevents pathogen entry, Synthesizes Vitamin D, Protection barrier.

Why would we dehydrate quickly without skin?

Skin acts like the cap of a water bottle — it prevents water loss from the body.

How does skin tone affect Vitamin D synthesis?

The darker the skin tone, the harder it is to convert sunlight into Vitamin D.

What are the components of the skeletal system?

Bones, Cartilage, Ligaments (bone to bone), Tendons (connect muscle to bone).

What is the function of ligaments?

Attach bone to bone.

What is the function of tendons?

Attach muscle to bone.

What are the main functions of the skeleton?

Structure, Protection of organs, Framework for movement.

What is the main physiology of the muscular system?

Contraction, Movement, Force production.

What types of muscle exist in the body?

Skeletal muscle (attached to bones), Cardiac muscle (heart), Smooth muscle (blood vessels, glands, organs).

What does smooth muscle in blood vessels do?

Helps maintain blood pressure.

What is NOT part of the muscular system: ligaments or tendons?

Ligaments are NOT part of the muscular system. They attach bone to bone — not muscle.

What are the two major divisions of the nervous system?

Central Nervous System (CNS) and Peripheral Nervous System (PNS).

What is sensory input?

Signals sent TO the CNS. Example: Feeling a table with your hand.

What is motor output?

Signals sent FROM the CNS to muscles/glands.

Why is the nervous system considered rapid response?

It responds immediately (ex: pulling hand off hot stove).

Describe the pathway of touching something hot.

Finger → PNS → CNS (brain/spinal cord) → signal back down → muscles move hand away.

What does the endocrine system control?

Hormones.

How does endocrine response compare to nervous system response?

Endocrine is slower. Nervous system is rapid.

What does the pineal gland secrete?

Melatonin.

What does the thyroid gland regulate?

Metabolic activity.

What does the pancreas release?

Digestive enzymes.

What do adrenal glands release?

Adrenaline.

What hormone do ovaries produce?

Estrogen.

What hormone do testes produce?

Testosterone.

What are the main functions of the cardiovascular system?

Delivers oxygen, Removes CO₂, Transports hormones, Transports drugs, Thermoregulation.

What happens in the lungs regarding blood?

Deoxygenated blood drops off CO₂ and picks up oxygen.

What color represents arteries? What do they carry?

Red — oxygenated blood.

What color represents veins? What do they carry?

Blue — deoxygenated blood.

What is the lymphatic system part of?

Immune system.

What does the lymphatic system filter for?

Pathogens (viruses, bacteria) and cancer cells.

What happens to lymph fluid after it is filtered?

It is returned to the heart and circulatory system.

Why might a lymph node in the armpit swell after a cut on the arm?

Lymph fluid drains there and traps infection.

What is the primary function of the respiratory system?

Gas exchange (O₂ in, CO₂ out).

What does the nasal cavity do?

Warms air, Filters air, Traps particles.

How does the respiratory system help with acid-base balance?

By regulating CO₂ levels.

Where does digestion begin?

In the mouth.

What does amylase do?

Breaks down starch into simpler sugars.

What is the path of food through the digestive system (basic)?

Mouth → Esophagus → Stomach → Intestines → Anus.

Why does the digestive system work closely with the cardiovascular system?

Nutrients are absorbed into the blood for transport.

What does KUB stand for?

Kidneys, Ureters, Bladder.

What are the main functions of the kidneys?

Filter blood, Eliminate waste, Regulate blood volume, Balance electrolytes, Control blood pressure, Regulate acid-base, Activate Vitamin D.

What are electrolytes?

Salts such as sodium, potassium, phosphorus, calcium.

What are gonads?

Organs that produce sex hormones and reproductive cells.

What hormones are required for reproduction?

Estrogen (female), Testosterone (male).

Do organ systems operate independently?

No. They are interdependent and cooperate to maintain homeostasis.

What would happen if the respiratory system failed?

No oxygen delivery → cardiovascular system fails → tissues die.

Why is absorption important in digestion?

Without absorption into blood, food would pass straight through without nourishing the body.