Human Blood Cells Overview

Red Blood Cells

• Red blood cells are crucial for delivering oxygen and removing waste.
• They contain hemoglobin, a protein that's bright red, which carries oxygen and carbon dioxide.
• Hemoglobin contains iron, enabling efficient oxygen transport.
• Red blood cells circulate throughout the body.
• Their average lifespan is 120 days.
• Bone marrow continually produces new red blood cells.
• The body re-circulates blood, rather than remaking it constantly.
• Mature red blood cells are flexible, biconcave disks without a nucleus or most organelles.
• Blood donation is safe for healthy adults.

White Blood Cells

• White blood cells (WBCs), also known as leukocytes, fight infection.
• Normal range in adults is 4,000 to 10,000 WBCs per microliter of blood.
• Increased WBC count indicates infection.
• Six main types: neutrophils (58%), eosinophils (2%), basophils (1%), bands (3%), monocytes (4%), lymphocytes (4%).
• Neutrophils are a primary defense against bacteria (ingest bacteria).
• Eosinophils fight parasites and participate in allergic reactions.
• Basophils are involved in allergic reactions, releasing histamine and heparin.
• Monocytes become macrophages and phagocytize bacteria and cellular debris throughout the body.
• WBCs use diapedesis to squeeze through blood vessel walls.
• Chemotaxis is the movement of WBCs toward areas of infection or inflammation.
• Phagocytosis is the process of ingesting and destroying pathogens.

Skin Cells

• Skin is the largest organ, acting as a protective barrier.
• Four main layers: epidermis, basement membrane, dermis, and subcutaneous layer.
• Epidermis (outermost layer) is microscopic, roughly 0.2 mm thick on the face.
• Epidermal cells regenerate every 28 days.
• Dermis (inner layer) is about 1.8 mm thick. Contains collagen, elastin, blood vessels, nerves, glands, and hair follicles.
• Skin functions include protection, preventing water loss/absorption, vitamin D production, temperature regulation, sensation (pain, touch), antigen presentation, and wound healing.

Bone Cells

• Bone cells are essential for bone growth, repair, and health.
• Specialized cells: osteoblasts (form new bone), osteoclasts (dissolve bone), osteocytes (maintain bone).

Muscle Cells

• Muscle cells (fibers) contract to produce movement and maintain posture.
• Three types: skeletal, cardiac, and visceral (smooth).
• Skeletal muscle cells, also known as striated muscle, are crucial for movement.
• Cardiac muscle (heart muscle) is involuntary.
• Visceral (smooth) muscle controls internal organs.

Sperm Cells

• Sperm are male reproductive cells that carry genetic material.
• Sperm cells have a head (acrosome, nucleus), midpiece (mitochondria), and tail (flagellum).
• The head carries genetic information.
• The midpiece provides energy.
• The tail propels the sperm for motility.
• Sperm life span can vary.

Fat Cells

• Fat cells have diverse functions beyond just storage.
• They provide warmth, protection for organs/tissues, and function in storage, and body temperature regulation and energy storage.
• Fat cells can produce a hormone called adiponectin.
• Obesity is linked to reduced adiponectin and increased risk of diseases.
• Fat cells are integral to energy balance, immune response, and temperature regulation. Fat cells come in two types: white (stores energy) and brown (produces heat) Fat cells play a role in smoothing out body contours.

Nerve Cells

• Nerve cells (neurons) are the basic units of the nervous system.
• Types include multipolar, bipolar, and pseudounipolar.
• Neutrons carry information rapidly using electrical and chemical signals.
• Main parts: cell body (nucleus), axons (send signals), and dendrites (receive signals).
• Transmission of signals occurs across synapses.