Three important features:

Stomach: food enters the stomach, breaks down by gastric juices, and then enters the...

Small Intestine: continues to break down by digestive enzymes from the pancreas and then goes to the....

Large Intestine: breaks down further and mixes with water to turn it into feces and prepares to enter the rectum.

Three critical features of the circulatory system are:

1. Heart: the heart, made of muscle and tissue, pumps blood and oxygen around the body and sends carbon dioxide back to the lungs.

2. Blood vessels: these transport oxygen, blood, nutrients and hormones throughout the body.

3. Arteries: stemming from the heart, carry oxygenated blood away from the heart to tissues, organs and cells. They are larger than blood vessels and branch out into slimmer sections (Bailey, 2019).

Three essential features of the respiratory system are:

1. Lungs: where oxygen comes in, and carbon dioxide is expelled during respiration. The lungs filter our debris and keep temperature and humidity regulated for the body.

2. Nasal Cavity: the point where oxygen enters the body and prepares it with humidity before it goes to the lungs.

3. Diaphragm: is a soft muscle that supports the lungs by contracting to draw air into the lungs and then relaxes to expel air. It is the primary muscle that assists in breathing (Professional, 2024a).

Three features of this system are:

1. Thyroid: is responsible for producing hormones that regulate metabolism and growth. It also influences the ovaries to produce hormones when it secrets thyroid hormones.

2. Ovaries: responsible for producing estrogen and progesterone and part of the reproductive system.

3. Pineal Gland: produces melatonin and helps regulate sleep.

Three important features to note are:

1. Femur: The femur, also known as the thigh bone, is the largest bone in the body and is located in the upper thigh area.

2. Gluteus Maximus: This is the largest muscle in the body and helps keep the body upright when walking or running. It is located in the buttocks and attaches to the gluteal tuberosity on the femur.

3. Achilles Tendon: This is the largest tendon in the human body and assists in walking and running. It is located at the back of the foot and extends towards the ankle and calf.

Three major components of this system are:

1. The Central Nervous System (CNS) comprises the brain and spinal cord.

2. The peripheral nervous system (PNS) is a complex system of nerves stemming from the spinal cord.

3. The Somatic Nervous System is in charge of voluntary movements like walking. The somatic nervous system works with the CNS by receiving messages from sensory neurons and then sending motor commands to initiate voluntary muscle movements.

Three important features of this system are:

1. Lymph nodes filter out infections and germs. These contain white blood cells that help fight infection.

2. Bone marrow: where immune-fighting blood cells are produced.

3. White blood cells are made in bone marrow, patrol the body, and fight infections by attacking foreign substances (Department of Health & Human Services, n.d.).

Three notable features of this system are:

1. Ovaries: produce hormones and eggs for menstruation or reproduction.

2. Hormone regulation: production of progesterone and estrogen by the ovaries to reproduce.

3. Fallopian tubes: transport eggs from the ovaries to the uterus.

Bailey, R. (2019, March 24). Types of Circulatory Systems: Open vs. Closed. ThoughtCo. https://www.thoughtco.com/circulatory-system-373576

Bailey, R. (2019b, November 25). Respiratory system and how we breathe. ThoughtCo. https://www.thoughtco.com/respiratory-system-4064891

Professional, C. C. M. (2024a, May 1). Respiratory system. Cleveland Clinic. https://my.clevelandclinic.org/health/body/21205-respiratory-system

ENDOCRINE SYSTEM. (n.d.). https://asapeducate.com/science_notes/endocrine-system/

American Board. (n.d.). https://americanboard.org/Subjects/biology/musculoskeletal-system/

Professional, C. C. M. (2024c, September 17). Nervous system. Cleveland Clinic. https://my.clevelandclinic.org/health/body/21202-nervous-system

The immune system. (2018, September 15). Immunodeficiency Canada. https://immunodeficiency.ca/primary-immunodeficiency/the-immune-system/

Department of Health & Human Services. (n.d.). Immune system explained. Better Health Channel. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/immune-system

      Healthdirect Australia. (n.d.). Female reproductive system. Healthdirect.     https://www.healthdirect.gov.au/female-reproductive-system