BIOL 2210L Unit 3: Integumentary System Authors: Terri Koontz and Megan Hancock, CNM Biology Department
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1 BIOL 2210L Unit 3: Integumentary System Authors: Terri Koontz and Megan Hancock, CNM Biology Department Creative Commons Attribution-NonCommercial 4.0 International License Terms to Know for Unit 3 Layers of the Integument Accessory Structures of the Skin Additional Instructor Terms Epidermis Hair follicle Dermis Hair root Hypodermis Hair shaft Arrector pili muscle Cells of the Epidermis Sebaceous glands Keratinocytes sebum keratin Sweat glands Melanocytes Meissner’s corpuscle melanin Pacinian corpuscle Layers of the Epidermis Layers of the Dermis Stratum basale Papillary layer Stratum spinosum dermal papillae Stratum granulosum Reticular Layer Stratum lucidum Stratum corneum Membranes Serous Membranes Specific Serous Membranes Mucous membranes (Mucosae) Serosa Parietal pericardium Serous membranes (Serosae) Serous fluid Visceral pericardium Cutaneous membrane Parietal serosa Parietal pleura Visceral serosa Visceral pleura Parietal peritoneum Visceral peritoneum Learning Objectives (modified from HAPS learning outcomes) 1. Membranes (mucous, serous, cutaneous) a. Describe the structure and function of mucous, serous, and cutaneous membranes. b. Describe locations in the body where each type of membrane can be found. 2. General functions of the skin & the subcutaneous layer a. Describe the general functions of the skin. b. Describe the general functions of the subcutaneous layer (also known as the hypodermis). 3. Gross & microscopic anatomy of skin a. With respect to the epidermis: i. Identify and describe the tissue type making up the epidermis. 2 ii. Identify and describe the layers of the epidermis, indicating which are found in thin skin and which are found in thick skin. iii. Correlate the structure of thick and thin skin with the locations in the body where each are found. b. Identify and describe the dermis and its layers, including the tissue types making up each dermal layer. 4. Roles of specific tissue layers of skin & the subcutaneous layer a. With respect to the epidermis: i. Describe the functions of the epidermis. ii. Explain how each of the five layers, as well as each of the following cell types and substances, contributes to the functions of the epidermis: stem cells of stratum basale, keratinocytes, melanocytes, keratin, and extracellular lipids. b. With respect to the dermis: i. Describe the overall functions of the dermis. c. With respect to the subcutaneous layer: i. Describe the functions of the subcutaneous layer. 5. Anatomy & functional roles of accessory structures a. With respect to the following - sweat glands (eccrine and apocrine), sebaceous glands, hair (follicle and arrector pili muscle), and sensory receptors (Meissner’s & Pacinian corpuscles and hair follicle receptor): i. Identify each structure. ii. Describe the location of each structure in the body. iii. Describe the anatomy of each structure. iv. Describe the function of each structure. Explanation of Anatomy In this lab, we will begin our study of membranes. A membrane is a simple organ that contains two tissue types: an epithelium and an underlying connective tissue. There are three covering membranes of the body: mucous, serous, and cutaneous. After learning about mucous and serous membranes, we will explore the cutaneous membrane in depth. The cutaneous membrane, our “skin”, is part of the integumentary system and serves as the boundary between our internal environment and the external world. Each layer of the skin has a functional role that aids in maintaining this boundary. The epidermis and dermis are discrete layers of skin that are themselves comprised of layers. There is a deep third layer of the integumentary system called the hypodermis, and this is not a true layer of the skin. We will finish the unit by exploring accessory structures of the integumentary system such as hair and glands. Think about how many internal diseases have manifestations on the skin that can be observed externally. Take a moment to consider how much time, effort, and money are devoted over the course of our lifetimes to grooming this organ. Our self-esteem is tied to how nice this organ looks. When a disease affects the skin’s appearance, it can be uncomfortable both physically and emotionally. What is acne? Why do we have a rash? Is there a cure for flaky skin? The skin can reflect our physical health and understanding the anatomy of this incredible organ can assist with providing patient care. Membranes Membranes of the body are simple organs. The definition of an organ is a structure that contains two or more tissues that perform a specific function. Membranes are comprised of two tissue types, making it a 3 “simple organ”. The two tissue types that make up membranes are epithelial and connective tissues. Membranes cover body areas and their primary function is protection. There are three types of covering membranes: mucous (mucosa), serous (serosa), and cutaneous. Mucous membranes are wet membranes, as they are bathed in fluid. Mucous membranes are associated with body tracts (i.e. digestive, respiratory, urinary, and reproductive tracts) that come into contact with the external environment. All mucous membranes contain stratified squamous epithelium in the areas that switch between the “internal” and external environment. This type of epithelium protects organ walls from abrasion as solid objects coming from the outside world come into contact with this membrane. Other types of epithelium found in mucous membranes reflect the function of a particular part of that organ system’s body tract. Mini Activity: Review epithelial tissues 1. What type of epithelial tissue is associated with the digestive system because it has the function of making large enzymatic proteins that chemically digest ingested food? 2. What type of epithelial tissue is associated with the respiratory system because it has the function of sweeping mucus, containing trapped inhaled debris, to the back of the throat? 3. What type of epithelial tissue is found only in the urinary system? The type of epithelial tissue in a mucous membrane varies according to the function of the body tract at a particular location along that tract. For example, the mucous membrane epithelia in the respiratory system are pseudostratified ciliated columnar epithelium (PCCE) in the nasal cavity and the large tubes of the lower respiratory system, stratified squamous in the throat region, simple columnar and simple cuboidal in the smaller tubes of the lower respiratory system, and simple squamous in the tiny air sacs where gas exchange occurs. Each epithelial tissue type is directly related to its function at that location. The connective tissue layer that all mucous membranes share is loose areolar connective tissue, which provides nutrients to the epithelium it underlies. The loose structure of areolar tissue allows for the quick diffusion of needed nutrients from the digestive and respiratory systems into the bloodstream. Serous membranes Serous membranes allow for internal organs to rub against one another in a relatively frictionless environment. The double layer membrane of serous membranes contains tissue types that are structured to perform diffusion: simple squamous epithelium and areolar connective tissue. The inner membrane of this double membrane attaches directly to the organ while the outer membrane attaches to the body cavity wall. The double layer serous membrane is also referred to as serosa. 4 Mini Activity: “Seeing” the double layering of serosa Take a piece of paper and fold it in half. Put the folded piece of paper on the table in front of you. Write parietal on the side that is not in contact with the table and write visceral on the side that is touching the table. The table represents an organ in the body. 1. What does visceral mean? 2. Now take your four fingers, which in this activity represent four ribs, and put them on top of the paper next to the word parietal. Ribs make up the wall of the thoracic body cavity. The word parietal is derived from a Latin word that means wall. Looking at the table, the folded paper, and your four fingers, can you correctly identify in the image below which letter represents the visceral serosa and which letter represents the parietal serosa? Write what you think are the correct identifications for those two serosal layers on the blank lines next to letters A and B. Image 1: Pleura Modified Creative Commons Attribution 4.0 International by Cancer Research UK uploader URL: Pleura The visceral serosa attaches to an organ. The word visceral means inner organ. The parietal serosa attaches to the body cavity wall. The space between these two serosal layers contains serous fluid. Serous fluid allows body organs to slip and slide against one another with very little friction, preventing abrasive forces that could cause organ damage. Specific serous membranes Three areas in the body have serous membranes: lungs, heart, and digestive organs. 5 The mini activity that you just did relates to the serosa surrounding the lungs (see Image 1). Lungs are encased in serous membranes specifically called pleura. The visceral pleura (labeled B.) directly attaches to the lung, whereas the parietal pleura (labeled A.) directly attaches to the thoracic body cavity wall. The serosa that surrounds the heart also has its own specific name called the pericardium. Peri- translates to “surrounds” (just like the perimeter of a building). Cardium means heart. The visceral pericardium directly attaches to the heart and the parietal pericardium is the outer serosal layer. Digestive organs are surrounded by their own serosa that is specifically called peritoneum. Visceral peritoneum attaches to digestive organs like the small intestines and stomach. The parietal peritoneum attaches to the abdominal body cavity wall. Layers of the Integument The integumentary system contains one of the largest organs of the body, the skin. The skin has a surface area of about one and half square meters and weighs approximately nine pounds, which is three times the weight of the average brain! The word integument means covering, and this external organ is our first line of defense against the world.