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9.1 Classification of joints Read Online
9.2 Fibrous joints Read Online
9.3 Cartilaginous joints Read Online
9.4 Synovial joints Read Online
9.5 Types of body movements Read Online
After this chapter, you will be able to:
The adult human body has 206 bones, and with the exception of the hyoid bone in the neck, each bone is connected to at least one other bone. Joints are the location where bones come together. Many joints allow for movement between the bones. At these joints, the articulating surfaces of the adjacent bones can move smoothly against each other. However, the bones of other joints may be joined to each other by connective tissue or cartilage. These joints are designed for stability and provide for little or no movement. Importantly, joint stability and movement are related to each other. This means that stable joints allow for little or no mobility between the adjacent bones. Conversely, joints that provide the most movement between bones are the least stable. Understanding the relationship between joint structure and function will help to explain why particular types of joints are found in certain areas of the body.
The articulating surfaces of bones at stable types of joints, with little or no mobility, are strongly united to each other. For example, most of the joints of the skull are held together by fibrous connective tissue and do not allow for movement between the adjacent bones. This lack of mobility is important, because the skull bones serve to protect the brain. Similarly, other joints united by fibrous connective tissue allow for very little movement, which provides stability and weight-bearing support for the body. For example, the tibia and fibula of the leg are tightly united to give stability to the body when standing. At other joints, the bones are held together by cartilage, which permits limited movements between the bones. Thus, the joints of the vertebral column only allow for small movements between adjacent vertebrae, but when added together, these movements provide the flexibility that allows your body to twist, or bend to the front, back, or side. In contrast, at joints that allow for wide ranges of motion, the articulating surfaces of the bones are not directly united to each other. Instead, these surfaces are enclosed within a space filled with lubricating fluid, which allows the bones to move smoothly against each other. These joints provide greater mobility, but since the bones are free to move in relation to each other, the joint is less stable. Most of the joints between the bones of the appendicular skeleton are this freely moveable type of joint. These joints allow the muscles of the body to pull on a bone and thereby produce movement of that body region. Your ability to kick a soccer ball, pick up a fork, and dance the tango depend on mobility at these types of joints.
Question: The papillary and reticular layers of the dermis are composed mainly of ________.
Choices:
melanocytes
keratinocytes
connective tissue
adipose tissue
Question: In response to stimuli from the sympathetic nervous system, the arrector pili ________.
Choices:
are glands on the skin surface
can lead to excessive sweating
are responsible for goose bumps
secrete sebum
Question: Sebaceous glands ________.
Choices:
are a type of sweat gland
are associated with hair follicles
may function in response to touch
release a watery solution of salt and metabolic waste
Question: Eccrine sweat glands ________.
Choices:
are present on hair
are present in the skin throughout the body and produce watery sweat
produce sebum
act as a moisturizer
Question: Langerhans cells are commonly found in the ________.
Choices:
stratum spinosum
stratum corneum
stratum granulosum
stratum basale
Question: Similar to the hair, nails grow continuously throughout our lives. Which of the following is furthest from the nail growth center?
Choices:
nail bed
hyponychium
nail root
eponychium
Question: In humans, exposure of the skin to sunlight is required for ________.
Choices:
vitamin D synthesis
arteriole constriction
folate production
thermoregulation
Question: The papillary layer of the dermis is most closely associated with which layer of the epidermis?
Choices:
stratum spinosum
stratum corneum
stratum granulosum
stratum basale
Question: Collagen lends ________ to the skin.
Choices:
elasticity
structure
color
UV protection
Question: The hair matrix contains ________.
Choices:
the hair follicle
the hair shaft
the glassy membrane
a layer of basal cells
Question: Which of the following is not a function of the hypodermis?
Choices:
protects underlying organs
helps maintain body temperature
source of blood vessels in the epidermis
a site to long-term energy storage
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