9.2 骨头
Section outline
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Are bones living?
::骨头还活着吗?It's common to think of bones as not living. But bones are very much living. In fact, you are constantly making new bone tissue . That means that you are also constantly getting rid of bone. Bone is full of , nerves , and all sorts of and , making it an extremely complex living tissue.
::人们通常认为骨头不是活的。但骨头是活的。事实上,你一直在制造新的骨骼组织。这意味着你也在不断地除掉骨头。骨骼充满了神经和各种种类的骨骼,使它成为一个极其复杂的活组织。Function and Structure of Bones
::Bones的功能和结构Many people think of bones as dry, dead, and brittle, which is what you might think if you saw a preserved skeleton in a museum. The association of bones with death is illustrated by the sweets shown in Figure . This is a common association because the calcium-rich bone tissue of a vertebrate is the last thing to decompose after the organism dies. However, the bones in your body are very much alive. They contain many tough protein fibers, are crisscrossed by , and certain parts of your bones are metabolically active. Preserved skeletons are cleaned with chemicals that remove all organic matter from the bones, which leaves only the calcium-rich, mineralized (hardened) bone tissue behind.
::许多人认为骨头是干枯的、死的和易碎的,如果你在博物馆里看到一个保存的骨骼,你会认为这是你所认为的。骨头与死亡的联系用图中显示的糖果来说明。这是一个常见的联系,因为脊椎动物的含钙骨头组织是生物体死后最后分解的东西。然而,你身体里的骨头非常活性。它们含有许多坚硬的蛋白质纤维,它们被切穿,而你骨骼的某些部分是代谢活性的。保存的骨骼被化学剂清洗干净,这些化学剂将所有有机物质从骨头中清除出来,这只留下富钙的、有矿化的(硬化的)骨骼组织。Sugar skulls made to celebrate Día de Los Muertos (Day of the Dead), a time (the 1 st and 2 nd of November) during which the people of Mexico and some Latin American countries celebrate and honor the lives of the deceased and celebrate the continuation of life. Skulls and bones are closely associated with death in many cultures.
::为了庆祝死亡日(Día de los Muertos),墨西哥和一些拉丁美洲国家人民在11月1日和2日庆祝和纪念死者生命并庆祝生命的延续。 在许多文化中,骨骼和骨头与死亡密切相关。Functions of Bones
::Bones 的函数函数As you read earlier in this lesson, your is important for the proper functioning of your body. In addition to giving shape and form to the body, bones have many other important functions:
::正如你在此课的前面所读到的,你对身体的正常运转很重要。除了给身体造成形状和形状外,骨骼还有其他许多重要功能:-
Structural support of the body: The skeleton supports the body against the pull of gravity. The large bones of the lower limbs support the trunk when standing.
::身体的结构支持: 骨骼支撑身体抵御引力的拉动。 下肢的大块骨头在立立时支持后备箱 。 -
Protection of internal
organs
: The skeleton provides a rigid frame work that supports and protects the soft organs of the body. The fused bones of the
cranium
surround the
brain
to make it less vulnerable to injury.
Vertebrae
surround and protect the
spinal cord
, and bones of the rib cage help protect the heart and
lungs
.
::保护内脏器官:骨骼提供了支持和保护身体软器官的僵硬框架工作。 脊椎骨的骨骼环绕大脑,使其更容易受伤。 脊椎围绕并保护脊髓,肋骨有助于保护心脏和肺部。 -
Attachment of the
: The skeleton provides attachment surfaces for muscles and
tendons
, which together enable
movement
of the body.
::外附:骨骼为肌肉和管子提供依附面,使身体能够移动。 -
Movement of the body: Bones work together with muscles as simple mechanical lever systems to produce body movement.
::身体运动:骨骼与肌肉一起工作,作为简单的机械操纵系统,产生身体运动。 -
Production of blood cells: The formation of blood cells takes place mostly in the interior (marrow) of certain types of bones.
::生产血细胞:血细胞的形成主要发生在某类骨骼的内部(骨髓)中。 -
Storage of
minerals
: Bones contain more
calcium
than any other organ in the form of calcium salts such as calcium phosphate. Calcium is released by the bones when blood levels of calcium drop too low. Phosphorus is also stored in bones.
::矿物储存:骨头含有的钙含量大于任何其他器官,其形式是钙盐,如磷酸钙;当钙的血液水平过低时,骨头释放的钙含量也高于任何其他器官;磷也储存在骨头中。
Structure of Bones
::骨头结构Although bones vary greatly in size and shape, they all have certain structural similarities. Bones are organs. Recall that organs are made up of two or more types of tissues. The two main types of bone tissue are compact bone and spongy bone . Compact bone makes up the dense outer layer of bones. Spongy bone is lighter and less dense than compact bone and is found toward the center of the bone. Periosteum (from peri = around and osteo = bone) is the tough, shiny, white membrane that covers all surfaces of bones except at the joint surfaces. Periosteum is composed of a layer of fibrous connective tissue and a layer of bone forming cells. These structures can be seen in Figure .
::虽然骨头大小和形状各异,但都具有一定的结构相似性。 Bones 是器官。 提醒注意器官由两种或两种以上的组织组成。 两个主要的骨骼组织类型是紧骨和海绵骨。 紧凑骨骼构成骨头密度大的外层。 结结壳骨比紧凑骨质轻,密度小, 并被发现在骨骼中心。 骨髓( 来自于周围 = 和骨骼 = 骨头 ) 是坚硬的、 亮亮亮的白膜, 覆盖骨骼的所有表面, 除了在共同表面。 骨骼由一层纤维连接组织和一层骨细胞组成。 这些结构可见于图中 。Bones consist of different types of tissue including compact bone, spongy bone, bone marrow , and periosteum.
::骨骼由不同种类的组织组成,包括紧骨、海绵骨、骨髓和皮下骨。-
Compact bone makes up the dense outer layer of bones. Its functional unit is the
osteon
.
Compact bone is very hard and strong.
::骨骼骨骼构成厚厚的骨骼外层,其功能单位是骨骼,骨骼骨骼非常硬和坚固。 -
Spongy bone is found inside bones and is lighter and less dense than compact bone. This is because spongy bone is porous.
::海绵骨在骨头中被发现,较轻,比紧凑骨密度小。这是因为海绵骨多孔。 -
Bone marrow
is a soft connective tissue that produces blood cells. It is found inside the pores of spongy bone.
::骨髓是一种产生血细胞的软连接组织,存在于海绵骨孔中。 -
Periosteum is a tough fibrous membrane that covers and protects the outer surfaces of bones.
::围膜是一种坚硬的纤维膜 覆盖并保护骨骼的外表面
The structure of a typical bone. The components that make up bones can be seen here. Compact bone is the dense material that makes up the outer ring of the bone. Most bones of the limbs, including the bones of the fingers, are long bones. The classification of “long bone” refers to the shape of the bone rather than to the size.
::典型骨头的结构。 骨骼的构成成分可以在这里看到。 骨骼骨骼是构成骨骼外环的稠密材料。 肢体的多数骨头,包括手指的骨头,都是长骨头。 “ 长骨头”的分类是指骨头的形状,而不是大小。The internal structure of a bone. Both compact and spongy bone can be seen.
::骨骼的内部结构 骨骼和海绵骨都可以看到Compact Bone
::压缩骨Just below the periosteum is the hard layer of compact bone tissue. It is so called due to its high density, and it accounts for about 80% of the total bone mass of an adult skeleton. Compact bone is extremely hard and is made up of many cylinder-shaped units called osteons, or Haversian systems. Osteons act like strong pillars within the bone to give the bone strength and allow it to bear the weight of the attached muscles and withstand the stresses of movement. As you can see in Figure , osteons are made up of rings of calcium salts and collagen fibers, called bone matrix . Bone matrix is a mixture of calcium salts, such as calcium phosphate and calcium hydroxide, and collagen fibers (a type of protein), which form hollow tubes that look similar to the rings on a tree. Each of these matrix tubes is a lamella, which means “thin plate” (plural: lamellae). The calcium salts form crystals that give bones great strength, but the crystals do not bend easily and tend to shatter if stressed. Collagen fibers are tough and flexible. All collagen fibers within a single lamella are lined up in the same direction, which gives each lamella great strength. Overall, the protein-calcium crystal combination in the matrix allows bones to bend and twist without breaking easily. The collagen fibers also act as a scaffold for the laying down of new calcium salts.
::骨质骨质由许多气瓶状的单位组成,称为骨质骨质,或Haversian系统。骨质骨质骨质骨质非常硬。骨质骨质骨质像坚固的柱子,可以让骨质坚固,使其承受附着肌肉的重量,并承受运动的压力。正如图所示,骨质骨质由高密度的钙盐和凝固纤维环组成,占成人骨质的80%左右。骨质骨质骨质骨质骨质骨质骨质骨质骨质骨质骨质骨质骨质骨质骨质骨质骨质骨质的混合体组成。骨质骨质骨质骨质骨质骨质骨质的硬性骨质骨质骨质骨质骨质骨质骨质骨质,骨质骨质骨质骨质骨质骨质的骨质骨质骨质骨质骨质骨质骨质骨质硬,骨质骨质骨质骨质骨质骨质骨质的骨质骨质硬,骨质骨质骨质骨质骨质骨质硬的骨质骨质骨质骨质骨质骨质结,骨质骨质骨质硬的骨质结结结,骨质骨质骨质骨质的骨质的骨质的骨质硬,骨质骨质结,骨质的骨质硬性骨质硬性骨质骨质骨质的骨质骨质的骨质的骨质的骨质骨质骨质的骨质骨质结、骨质的骨质的骨质的骨质的骨质结。。。。。骨质结、骨质结、骨质结、骨质、骨质的骨质结、骨质的骨质的骨质的骨质的骨质的骨质结、骨质结、骨质的骨质的骨质的骨质的骨质的骨、骨质的骨质的骨质的骨质的骨质的骨质的骨质、骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨、骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨质的骨质In the center of each osteon is a Haversian canal. The canal serves as a passageway for blood vessels and nerves. Within each osteon, many bone cells called osteocytes are located. Osteocytes are found in little pockets called lacunae that are sandwiched between layers of bone matrix. You can see lamellae and osteocytes in their lacunae in Figure . Osteocytes are responsible for monitoring the protein and mineral contents of the bone, and they direct both the release of calcium into the blood and the uptake up of calcium salts into the bone. Other bone cells, called osteoblasts, secrete the organic content of matrix and are responsible for the growth of new bone. Osteoblasts are found near the surface of bones. Osteoclasts are bone cells that remove calcium salts from bone matrix. These bone cells will be discussed in further detail later in this lesson. In the meantime, Table describes some of the different structures and functions of bones.
::每个骨骼的中心是哈弗斯运河,运河是血管和神经的通道。在每头骨骼中,有许多被称为骨质细胞。骨质细胞存在于小口袋中,叫做骨质基体层之间的缝隙。可以看到在图中,利氏体和骨质细胞的空隙中。骨质细胞负责监测骨头的蛋白质和矿物质含量,它们指导将钙释放到血液中,并将钙盐吸收到骨头中。其他骨质细胞,叫做“骨质细胞”,隐藏矩阵中的有机成分,并负责新骨头的生长。在骨质表面附近发现了骨质细胞。骨质细胞是从骨质基体中去除钙盐的骨细胞。这些骨质细胞将在本课稍后进一步详细讨论。同时,表格描述了骨质的一些不同结构和功能。Function Location Osteons (also known as Haversian systems) Act like pillars to give bones strength. Compact bone Bone matrix A mixture of calcium salts and collagen fibers that form hollow tubes that look similar to the rings on a tree. Compact bone and spongy bone Lamella Layers of bone matrix in which collagen fibers point in the opposite direction of the fibers of the lamellae to each side, offering great strength and flexibility. Are the “tree rings” of osteons Lacunae Location of osteocytes. Between lamellae of bone matrix Osteocytes Monitor the protein and mineral contents of bones and direct both the release of calcium into the blood and the uptake up of calcium salts into the bone. Within lacunae of osteons Osteoblasts Bone-forming cells that secrete organic parts of matrix (collagen). Found near the surface of bones Osteoclasts Responsible for the breakdown of matrix and the release of calcium salts into the blood. Bone surfaces Chondrocyte Cartilage-forming cell. Periosteum Contains pain receptors and is sensitive to pressure or stress. It provides both nourishment through a good supply of blood and an attachment for muscles and tendons. Collagen fibers Tough protein fibers that give bones flexibility and prevent shattering. Calcium salts Form crystals that give bones great strength. The locations of Haversian canals and osteocytes in osteons of compact bone.
::哈弗斯运河和骨质骨质骨质骨质骨质骨质中的骨质疏松物的位置。Spongy Bone
::海绵骨Spongy bone occurs at the ends of long bones and is less dense than compact bone. The term “spongy” refers only to the appearance of the bone, as spongy bone is quite strong. The lamellae of spongy bone form an open, porous network of bony branches, or beams, called trabiculae, that give the bone strength and make the bone lighter. This also allows room for blood vessels and bone marrow. Spongy bone does not have osteons; instead, nutrients reach the osteocytes of spongy bone by through tiny openings in the surface of the spongy bone. Spongy bone makes up the bulk of the interior of most bones including the vertebrae.
::“海绵”一词仅指骨头的外观,因为海绵骨头相当坚固。海绵骨头的瘸子形成一个开放的、多孔的肉枝网,或称为三毛球的梁,它能提供骨头的强度并使骨质更轻。这也为血管和骨髓提供了空间。海绵骨头没有;相反,营养素通过海绵骨头表面的小开口到达海绵骨头的骨骨骨骨骨骨骨骨。海绵骨构成包括脊椎在内的大多数骨骼的内部大部分。Bone Marrow
::骨骨髓Many bones also contain a soft connective tissue called bone marrow. There are two types of bone marrow: red marrow and yellow marrow. Red marrow produces red blood cells , platelets , and most of the white blood cells for the body. Yellow marrow produces white blood cells. The color of yellow marrow is due to the high number of fat cells it contains. Both types of bone marrow contain numerous blood vessels and capillaries. In newborns, bones contain only red marrow. As the child ages, red marrow is mostly replaced by yellow marrow. In adults, red marrow is mostly found in the flat bones of the skull, the ribs, the vertebrae, and pelvic bones. It is also found between the spongy bone at the very top of the femur and the humerus.
::许多骨骼还含有一个称为骨髓的软结组织。 有两种骨髓:红骨髓和黄色骨髓。红骨髓产生红血细胞、小板骨和大部分身体白血细胞。黄骨产生白色血细胞。黄骨是黄骨的产物。黄骨的颜色是因为它含有大量脂肪细胞。两种骨髓都含有许多血管和刺青。在新生儿中,骨头只含有红骨。随着孩子的老化,红骨髓大部分被黄色骨髓所取代。在成年人中,红骨大多存在于头、肋骨、脊椎和骨骨骨骨骨的平板骨骨中。它也存在于股骨顶的海绵骨和骨之间。Periosteum
::Periosteum( Perioteum) Periosteum( Perioteum)The outer surfaces of bones—except where they make contact with other bones at joints—are covered by periosteum. Periosteum has a tough, external fibrous layer and an internal layer that contains osteoblasts (the bone-growing cells). The periosteum is richly supplied with blood, lymph , and nociceptors, which make it very sensitive to manipulation (recall that nociceptors are pain receptors that are also found in the skin and skeletal muscles). Periosteum provides nourishment to the bone through a rich blood supply. The periosteum is connected to the bone by strong collagen fibers called Sharpey's fibres, which extend into the outer lamellae of the compact bone.
::骨骼的外表——除与其他骨骼接合处的外表外——都由皮下骨骼覆盖;骨下骨有坚硬的外部纤维层和内层,内层含有骨质(骨质生长细胞);骨下骨层充斥着血液、淋巴和鼻孔,对操纵非常敏感(请注意,非受体是疼痛受体,皮肤和骨骼肌肉中也有这种受体);骨下骨通过丰富的血液供应为骨头提供营养;骨下骨通过称为Sharpey纤维的强烈凝固凝固的凝固纤维与骨相连,这些纤维延伸至紧凑骨的外脊椎。Bone Shapes
::骨形状The four main types of bones are long, short, flat, and irregular. The of a bone as being long, short, flat, or irregular is based on the shape of the bone rather than the size of the bone. For example, both small and large bones can be classified as long bones. There are also some bones that are embedded in tendons; these bones tend to be oval-shaped and are called sesamoid bones.
::骨骼的四大类型是长的、短的、平的和不固定的。骨骼的长的、短的、平的或不固定的都是根据骨头的形状而不是骨头的大小。例如,大小的骨头可以分为长的骨头。还有一些骨头嵌在圆锥中;这些骨头的形状往往是奥瓦尔形的,被称为赛索骨。-
Long Bones:
Bones that are longer than they are wide are called long bones. They consist of a long shaft with two bulky ends. Long bones are primarily made up of compact bone, but may also have a large amount of spongy bone at both ends. Long bones include bones of the thigh (femur), leg (tibia and fibula), arm (humerus), forearm (ulna and radius), and fingers (phalanges). The classification refers to the shape rather than the size.
::长骨:长于宽度的骨骼被称为长骨,由两条大腿的长轴组成,长骨主要由紧骨组成,但两端也可能有大量的海绵骨。长骨包括大腿骨(femur)、腿(tibia和fibula)、臂(humerus)、前臂(ulna和半径)和手指(phalanges)的骨骼。分类是指形状而不是大小。 -
Short Bones:
Short bones are roughly cube-shaped and have only a thin layer of compact bone surrounding a spongy interior. The bones of the wrist (carpals) and ankle (tarsals) are short bones, as are the sesamoid bones (see below).
::短骨:短骨大致是立方形,在海绵内部周围只有一层薄骨,手腕骨(颈部)和脚踝骨是短骨,骨也是短骨(见下文)。 -
Sesamoid Bones:
Sesamoid bones are embedded in tendons. Since they act to hold the tendon farther away from the joint, the angle of the tendon is increased and thus the force of the muscle is increased. An example of a sesamoid bone is the patella (kneecap).
::骨: 骨嵌入骨中。 由于它们采取行动将骨拖得离结骨更远, 角的角会增大, 肌肉的强度也因此增加。 骨的一个例子就是骨( 骨 ) 。 -
Flat Bones:
Flat bones are thin and generally curved, with two parallel layers of compact bone sandwiching a layer of spongy bone. Most of the bones in the skull (cranium) are flat bones, as is the sternum (breastbone).
::扁骨头:扁骨头是薄的,一般是弯曲的,有两层平行的紧凑骨头,在海绵骨头层中做两层三明治。 头骨(头骨)中的大多数骨头是扁骨头,胸骨(胸骨)也是扁骨头。 -
Irregular Bones:
Irregular bones are bones that do not fit into any of the above categories. They consist of thin layers of compact bone surrounding a spongy interior. As implied by the name, their shapes are irregular and complicated. The vertebrae and pelvis are irregular bones.
::非正常骨骼:非正常骨骼是不属于上述任何类别的骨骼,由海绵内部的细细紧凑骨骼组成,如名称所暗示的,其形状是不正常和复杂的,脊椎骨和骨盆是不正常的骨骼。
All bones have surface markings and characteristics that make a specific bone unique. There are holes, depressions, smooth facets, lines, projections, and other markings. These usually represent passageways for vessels and nerves, points of articulation with other bones, or points of attachment for tendons and ligaments .
::所有骨头都有表层标记和特征,使特定的骨头具有独特性,有洞、抑郁、光滑的侧面、线条、投影和其他标记,通常代表船只和神经的通道、与其他骨头的连接点或圆形和颈部的连接点。Cellular Structure of Bone
::Bone 的细胞结构When blood calcium levels decrease below normal, calcium is released from the bones so that there will be an adequate supply for metabolic needs. When blood calcium levels are increased, the excess calcium is stored in the bone matrix. The dynamic process of releasing and storing calcium goes on almost continuously and is carried out by different bone cells.
::当血液中的钙含量降低到正常水平以下时,从骨头中释放出钙,从而满足代谢需要。当血液中的钙含量增加时,多余的钙储存在骨骼基体中。释放和储存钙的动态过程几乎持续进行,由不同的骨细胞进行。There are several types of bone cells:
::骨细胞有几种类型:-
Osteoblasts are bone-forming cells that are located on the inner and outer surfaces of bones. They make a collagen-rich protein mixture (called osteoid), which mineralizes to become bone matrix. Osteoblasts are immature bone cells. Osteoblasts that become trapped in the bone matrix differentiate into osteocytes. The osteocytes stop making osteoid and instead direct both the release of calcium from the bones and the uptake of calcium from the blood.
::骨质激素是骨质外表和骨质外表的骨质形成细胞,形成富钴蛋白混合物(称为骨质素),将蛋白质矿化成为骨质基体;骨质激素是不成熟的骨质细胞;被困在骨质基中的骨质激素分为骨质素。骨质素停止制造骨质素,而是引导骨头中的钙释放和血液中的钙吸收。 -
Osteocytes originate from osteoblasts that have migrated into, and become trapped and surrounded by, bone matrix, which they themselves produce. The spaces that they occupy are known as lacunae. Osteocytes are star-shaped, and they have many processes that reach out to meet osteoblasts probably for the purposes of
. Their functions include matrix maintenance and calcium
. They are mature bone cells. Refer to
Figure
for the location of osteocytes.
::骨骼细胞源自已经迁移到骨质基体中、并被其困住和环绕在骨质基体中的骨质球体,它们自己产生的骨质基体。它们占据的空间被称为空隙。骨质细胞是恒星形的,它们有许多过程可以达到骨质球,可能是为了...的目的。它们的功能包括矩阵维护和钙。它们是成熟的骨细胞。参考骨质细胞位置的图表。 -
Osteoclasts are the cells responsible for bone resorption, which is the remodeling of bone to reduce its volume (see below). Osteoclasts are large cells with many
and are located on bone surfaces. They secrete acids that dissolve the calcium salts of the matrix, releasing them into the blood stream. This causes the calcium and phosphate concentrations of the blood to increase. Osteoclasts constantly remove minerals from the bone, and osteoblasts constantly produce matrix that binds minerals into the bone, so both of these cells are important in calcium homeostasis.
::骨骼吸附是骨骼吸附的细胞,即骨骼的改造,以减少其体积(见下文)。骨骼吸附是许多大细胞,分布在骨头表面。它们分泌酸,溶解基体中的钙盐,将其释放到血液中。这导致血液的钙和磷酸盐浓度增加。骨骼吸附不断从骨头中移除矿物,骨骼吸附不断产生将矿物结合到骨头中的基质,因此这两种细胞在钙软骨中都很重要。
Bone Cells and Calcium Homeostasis
::骨细胞和钙Remodeling, or bone turnover, is the process of resorption of minerals followed by replacement by bone matrix, which causes little overall change in the shape of the bone. This process occurs throughout a person's life. Osteoblasts and osteoclasts communicate with each other for this purpose. The purpose of remodeling is to regulate calcium homeostasis, repair micro-damaged bones (from everyday stress), and shape the skeleton during skeletal growth.
::重塑或骨质更替是矿物再吸附的过程,然后取而代之的是骨质矩阵,这在骨头的形状上几乎没有什么整体变化。这一过程贯穿于一个人的整个生命中。为此目的,骨骼和骨骼相互交流。改造的目的是调节钙软骨,修复(日常压力产生的)微损伤骨骼,并在骨骼发育期间塑造骨骼。The process of bone resorption by the osteoclasts releases stored calcium into the systemic circulation and is an important process in regulating calcium balance . As bone formation actively fixes circulating calcium in its mineral form by removing it from the bloodstream, resorption actively unfixes it, thereby increasing circulating calcium levels. These processes occur in tandem at site-specific locations.
::骨质激素的骨吸附过程将存储的钙释放到系统循环中,这是调节钙平衡的一个重要过程,因为骨质形成通过将钙从血液中取出,积极修补以矿物形式流通的钙,从而积极重新吸附,使其解密,从而增加循环的钙水平,这些过程同时在特定地点发生。Summary
::摘要-
Under the direction of osteocytes, osteoblasts continuously build up bone, while osteoclasts continuously break down bone to maintain mineral homeostasis.
::在骨质素的指导下,骨质激素不断积累骨骼,而骨质素则不断分解骨骼,以保持矿物的均匀性。 -
Bone tissues include compact bone, spongy bone, bone marrow, and periosteum.
::骨骼组织包括紧骨、海绵骨、骨髓和围骨。
Review
::回顾-
List three functions of bone.
::列出骨的三个函数。 -
Compare long bones to short bones.
::长骨头和短骨头比起来 -
Give two examples of long bones.
::举两个长骨头的例子 -
Compare and contrast the structures and functions of compact bone and spongy bone.
::对比和对比紧凑骨骼和海绵骨的结构和功能。 -
Explain how bones maintain mineral homeostasis in the body.
::解释骨头如何保持 矿物质在身体的常态。
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Structural support of the body: The skeleton supports the body against the pull of gravity. The large bones of the lower limbs support the trunk when standing.
