bio review

Vertebrates and Invertebrates

• Vertebrates have a backbone, belonging to Phylum Chordata, with classes Agnatha, Osteichthyes, and others.
• Invertebrates lack a backbone.

Vertebrate Skeletal Systems

• Cartilaginous fishes (sharks) have skeletons made of cartilage.
• Other vertebrates have skeletons composed of both cartilage and bone.

Vertebral Column

• The backbone supports the body and serves as an attachment point for muscles.
• It protects the spinal cord, which runs through a canal inside it.
• The vertebral column consists of individual vertebrae with intervertebral disks (cartilage) between them, acting as shock absorbers and flex points.

Exoskeleton vs Endoskeleton

• Exoskeletons are external body parts that receive the force of muscle contractions, found in animals like grasshoppers, cockroaches, crustaceans, and lobsters.
• Endoskeletons are internal frameworks of hard parts, found in vertebrates.

Bone Anatomy

• Adult humans have 206 bones, ranging in size from the middle ear bones to the massive femur (thighbone).
• Long bones (e.g., femur, limb bones) have osteons, bone cells (osteocytes), and an extracellular matrix containing protein collagen and hardened by calcium and phosphorus deposits.
• Cancellous bone (spongy bone) is strong yet lightweight, with a matrix containing many cavities.
• Cortical bone (compact bone) is dense and makes up the shaft of long bones, consisting of many concentric rings of mineralized bone tissue with living bone cells in between.
• Periosteum is a dense irregular connective tissue enveloping bones, except for the surface of joints.

Bone Cells

• There are four cell types in bones:
  • Osteogenic cells (undifferentiated stem cells that develop into osteoblasts)
  • Osteoblasts (form bone matrix)
  • Osteocytes (maintain bone tissue)
  • Osteoclasts (resorb bone)

Ossification (Bone Formation)

• Intramembranous ossification occurs on or within fibrous connective tissues, leading to bone formation in the skull and other areas.
• Endochondral ossification occurs in cartilage, contributing to longitudinal growth and replaced by bone in most bones.

Joints

• Functional classes of joints:
  • Immoveable joints
  • Slightly moveable joints
  • Freely moveable joints
• Joint diseases:
  • Sprains (overstretched or torn ligaments)
  • Torn meniscus (in the knee)
  • Osteoporosis (bone loss outpacing bone formation)
  • Arthritis (chronic inflammation)

Muscular System

• Skeletal muscles are voluntary and have functions like:
  • Stretch reflex
  • Regulating body temperature
  • Attachment (e.g., the diaphragm)

Alveoli

• Alveoli are thin-walled pockets where gas exchange occurs.
• Slightly oily surfactant prevents alveolar walls from collapsing and sticking together.
• Oxygen is higher in the alveoli and CO2 is higher in the capillaries.
• Gas exchange occurs at the lungs and in body cells, moving oxygen into cells and CO2 out.

Cardiovascular System

• Blood flow:
  • Oxygenated blood from the lungs returns to the heart via the pulmonary veins.
  • Deoxygenated blood from the body returns to the heart via the superior and inferior vena cava.
• Blood pressure:
  • Systolic pressure: highest when the heart contracts during ventricular systole.
  • Diastolic pressure: lower pressure when the ventricles are relaxed.
  • Homeostatic mechanisms regulate arterial blood pressure by altering arteriole diameter.

Lymphatic System

• The adult human body loses 4-8 L of fluid from capillaries to surrounding tissues.