Chap 40 skin and skeletal-SM23

Chapter 40: Body Surface, Protection, and Specialized Cells

Overview

This chapter focuses on the structure and functions of epithelial tissue and the integumentary systems in various organisms, drawing connections with relevant concepts introduced in Chapter 32. Epithelial tissues serve critical roles in protection, secretion, absorption, and sensation across diverse biological taxa.

Learning Objectives

Epithelial Tissue and Integumentary Systems

• Structure & Function: Understand and compare how epithelial tissues are structured and function across various organisms, including their roles in providing protection and facilitating exchange between the body and the external environment.

• Epithelial Secretions: Explore different types of epithelial secretions such as cuticles (waterproof coverings) and shells in animals, which serve protective functions and help retain moisture in terrestrial environments.

Syncytial Epidermis

• Definition: Define syncytial epidermis as a type of epithelial tissue characterized by multiple nuclei within a single cell membrane. This can be observed in some insect larvae and certain marine mollusks, contributing to their adaptive survivability.

Vertebrate Skin Structure

• General Anatomy: Describe the multilayered structure of vertebrate skin, including the epidermis, dermis, and hypodermis, along with the various cell types (keratinocytes, melanocytes, etc.) contributing to key functions like protection and thermoregulation.

Epidermis vs Dermis

• Structural Differences: Analyze the distinct structural features and functions of the epidermis (outermost layer responsible for barrier function) versus the dermis (inner layer containing blood vessels, nerves, and connective tissue), including the role of collagen and elastin fibers in providing skin strength and elasticity among vertebrates.

Types of Burns

• Classification: Identify and describe four types of burns:

  • First-degree burns: Affect only the epidermis, causing redness and minor pain.

  • Second-degree burns: Involve the epidermis and part of the dermis, leading to blisters and more intense pain.

  • Third-degree burns: Extend through the dermis into subcutaneous tissue; they may appear white or charred and can be painless due to damage to nerve endings.

Skin Cancers

• Types: Recognize three main types of skin cancer, stemming from different skin cells:

  • Basal Cell Carcinoma: Arises from basal cells and is the most common type, typically appearing as a pearly or waxy bump.

  • Squamous Cell Carcinoma: Develops from squamous cells and can be more aggressive than basal cell carcinoma, presenting as red, scaly patches or open sores.

  • Malignant Melanoma: The deadliest skin cancer type, characterized by changes in moles or the appearance of new pigmented lesions, requiring early detection for effective treatment.

Skeletal System

Functions of a Skeleton

• Overview: The skeleton provides essential functions including:

  • Support: Offering a structural framework for the body.

  • Protection: Shielding vital organs (e.g., skull for the brain, ribcage for lungs).

  • Movement: Facilitating movement through muscle attachments.

  • Storage: Storing minerals (e.g., calcium and phosphorus) and lipids in fatty tissues.

  • Blood Cell Formation: The red marrow produces blood cells through hematopoiesis.

Types of Animal Skeletons

• Classification: Distinguish between the following types of skeletons:

  • Hydrostatic Skeleton: Utilizes fluid-filled compartments that provide rigidity and enable flexibility (e.g., in jellyfish and earthworms).

  • Exoskeleton: A hard external covering that protects organisms (e.g., arthropods like crabs and insects).

  • Endoskeleton: An internal skeletal structure characteristic of vertebrates, made of bone and cartilage that supports larger body mass.

Divisions of the Vertebrate Skeleton

• Axial Skeleton: Comprised of the skull, vertebral column, and rib cage, forming the central axis of the body.

• Appendicular Skeleton: Involves the limbs (arms and legs) and girdles (shoulder and pelvic), allowing for movement and manipulation of the environment.

Bone Types

• Classification: Differentiate between types of bones:

  • Dense (Compact) Bone: The outer layer providing strength and support.

  • Spongy Bone: The inner layer, less dense, containing trabecular structures and housing bone marrow.

Bone Marrow Types

• Functionality: Identify distinct types of bone marrow:

  • Red Marrow: Responsible for hematopoiesis, producing red blood cells, white blood cells, and platelets.

  • Yellow Marrow: Comprised of adipose tissue, serving primarily as an energy reserve.

Structural Types of Bones

• Long Bones: Longer than wide; examples include femur and humerus, which support weight and facilitate movement.

• Short Bones: Cuboidal shapes, like carpals of the wrist, providing stability and support.

• Flat Bones: Thin, flattened structures, such as those found in the skull, offering protection and broad surfaces for muscle attachment.

Anatomical Regions of Long Bones

• Epiphysis: The end regions of long bones that articulate with other bones, typically covered by articular cartilage.

• Diaphysis: The shaft of the bone, providing leverage and structural support.

• Metaphysis: The growth zone located between the diaphysis and epiphysis; crucial during bone development.

Bone Formation Types

• Endochondral Formation: Involves the replacement of cartilage with bone, typical in long bone development.

• Intramembranous Formation: Bones form directly from connective tissue, often seen in flat bones like the skull.

Types of Joints and Movements

• Joint Types:

  • Synovial Joints: Freely movable joints, contained within a fluid-filled capsule; examples include the knee and shoulder.

  • Fibrous Joints: Bound by dense connective tissue, mostly immobile (e.g., sutures in the skull).

  • Cartilaginous Joints: Allow limited movement, connected by cartilage (e.g., intervertebral discs).

• Joint Movements:

  • Flexion: Reducing the angle between body parts (e.g., bending the elbow).

  • Extension: Increasing the angle between body parts (e.g., straightening the elbow).

  • Hyperextension: Angling beyond normal limits (e.g., bending the neck back).

  • Abduction: Movement away from the body’s midline (e.g., lifting arms sideways).

  • Adduction: Movement towards the body’s midline (e.g., lowering arms to the sides).