Fundamentholfundamenthol

Skeletal System

BiologyLocomotion and MovementFor NEET aspirants

The skeletal system is the framework of bones and a few cartilages that supports the body and makes movement possible. This page covers all 206 bones of the human skeletal system: the axial skeleton (skull, vertebral column, sternum and ribs) and the appendicular skeleton (limb bones and girdles), with the bone count of every region. It follows the NCERT Class 11 chapter Locomotion and Movement. NEET often asks the number of bones in each region, the types of ribs and the bones of the girdles.

On this page1Bone and cartilage2Axial skeleton3Skull4Vertebral column5Sternum and ribs6Limb bones7Girdles8Exam essentials9Quick revision10Solved examples11Practice
Key Points at a Glance
  1. ★ Must learn Human skeleton: 206 bones and a few cartilages, in two divisions: axial (80 bones) and appendicular.
  2. Bone: very hard matrix due to calcium salts. Cartilage: slightly pliable matrix due to chondroitin salts.
  3. ★ Must learn Skull = 22 bones: 8 cranial + 14 facial. Also a U-shaped hyoid, and 3 ear ossicles in each middle ear.
  4. Dicondylic skull: two occipital condyles articulate with the first vertebra, the atlas.
  5. ★ Must learn Vertebral column: 26 vertebrae = cervical 7, thoracic 12, lumbar 5, sacral 1 (fused), coccygeal 1 (fused).
  6. Seven cervical vertebrae occur in almost all mammals, including human beings.
  7. ★ Must learn 12 pairs of ribs, each bicephalic: true ribs 1-7, false (vertebrochondral) ribs 8-10, floating ribs 11-12.
  8. Rib cage = thoracic vertebrae + ribs + sternum.
  9. ★ Must learn Each limb has 30 bones. Fore limb: humerus, radius, ulna, 8 carpals, 5 metacarpals, 14 phalanges.
  10. Hind limb: femur (longest bone), tibia, fibula, 7 tarsals, 5 metatarsals, 14 phalanges and the patella.
  11. Pectoral girdle half = clavicle + scapula; the glenoid cavity and head of the humerus form the shoulder joint.
  12. Pelvic girdle = 2 coxal bones (each ilium + ischium + pubis); acetabulum receives the femur; pubic symphysis has fibrous cartilage.

1. Skeletal System: An Overview

  • The skeletal system consists of a framework of bones and a few cartilages.
  • It has a significant role in the movements shown by the body. Chewing needs the jaw bones; walking needs the limb bones.
  • Bone and cartilage are specialised connective tissues.
Bone
  • Very hard matrix
  • Hardness due to calcium salts
Cartilage
  • Slightly pliable matrix
  • Pliability due to chondroitin salts
★ Very important The human skeletal system is made of 206 bones and a few cartilages. It has two principal divisions: the axial skeleton and the appendicular skeleton.
Key idea
Bones (hard, calcium salts) and cartilages (pliable, chondroitin salts) form a 206-bone skeleton in two divisions, axial and appendicular.

2. Axial Skeleton

  • ★ Exam imp The axial skeleton has 80 bones distributed along the main axis of the body.
  • The skull, vertebral column, sternum and ribs make up the axial skeleton.

Counting the 80 axial bones

PartNumber of bones
Skull (cranial 8 + facial 14)22
Hyoid1
Ear ossicles (3 in each middle ear)6
Vertebral column26
Sternum1
Ribs (12 pairs)24
Total80
Memory Trick

Axial total: 22 + 1 + 6 + 26 + 1 + 24 = 80 (skull, hyoid, ear ossicles, vertebrae, sternum, ribs).

2.1 Skull

  • The skull is made of two sets of bones, cranial and facial, which total 22 bones.
  • ★ Exam imp Cranial bones are 8 in number. They form the hard protective outer covering of the brain, the cranium.
  • The facial region is made up of 14 skeletal elements, which form the front part of the skull.
  • Hyoid: a single U-shaped bone at the base of the buccal cavity.
  • Each middle ear contains three tiny bones, malleus, incus and stapes, together called ear ossicles.
  • The skull articulates with the superior region of the vertebral column with the help of two occipital condyles. So the human skull is dicondylic.
Human skull, side view, with the hyoid bone Side view of a human skull. The frontal, parietal, temporal and occipital bones form the rounded cranium. The sphenoid and ethmoid, also cranial bones, show around the eye socket, while the lacrimal, nasal and zygomatic bones, the maxilla and the mandible form the face. The hyoid bone lies on its own below the mandible. Parietal bone Occipital bone Temporal bone Frontal bone Sphenoid bone Nasal bone Ethmoid bone Lacrimal bone Zygomatic bone Maxilla Mandible Hyoid bone
Figure 1: Human skull (diagrammatic). The cranial bones enclose the brain, the facial bones form the front of the skull, and the U-shaped hyoid lies separately below the mandible.
Extra Depth: Of the bones labelled in Figure 1, the frontal, parietal, temporal, occipital, sphenoid and ethmoid are cranial bones (8 in all, as the parietal and temporal are paired). The nasal, lacrimal, zygomatic, maxilla and mandible are facial bones.
Memory Trick

Ear ossicles from the eardrum inwards, M-I-S: Malleus, Incus, Stapes. Three in each ear, so 6 in all.

2.2 Vertebral column

  • The vertebral column is formed by 26 serially arranged units called vertebrae, and is placed dorsally.
  • It extends from the base of the skull and forms the main framework of the trunk.
  • Each vertebra has a central hollow portion, the neural canal, through which the spinal cord passes.
  • ★ Exam imp The first vertebra is the atlas; it articulates with the occipital condyles.
  • Starting from the skull, the column is differentiated into five regions:

Regions of the vertebral column

RegionNumber of vertebrae
Cervical7
Thoracic12
Lumbar5
Sacral1 (fused): sacrum
Coccygeal1 (fused): coccyx
Total26
  • The number of cervical vertebrae is seven in almost all mammals, including human beings.
  • Functions: it protects the spinal cord, supports the head, and is the point of attachment for the ribs and the musculature of the back.
Vertebral column, right side view Side view of the human vertebral column from the right, showing its gentle S-shaped curves. From the top come the 7 cervical vertebrae, starting with the atlas, then the 12 thoracic vertebrae and the 5 lumbar vertebrae, with an intervertebral disc between neighbouring vertebrae. The first and last vertebra of each region are marked. The fused sacrum and the small coccyx form the lower end. Cervicalvertebrae (7) Thoracicvertebrae (12) Lumbarvertebrae (5) Atlas (C1) C7 T1 Intervertebraldisc T12 L1 L5 Sacrum Coccyx
Figure 2: Vertebral column (right lateral view). Cervical, thoracic and lumbar vertebrae lie above the sacrum and coccyx, with intervertebral discs between the vertebrae.
Memory Trick

Breakfast at 7, lunch at 12, dinner at 5: 7 cervical, 12 thoracic, 5 lumbar; then 1 sacrum and 1 coccyx, each fused, giving 26.

NEET Focus
  • Adult count is 26 because the sacral and coccygeal vertebrae are each counted as one fused unit.
  • The atlas is the first vertebra and articulates with the occipital condyles; two condyles make the skull dicondylic.
  • "Seven cervical vertebrae" holds for almost all mammals; a statement saying "all mammals" is too strong.
  • The hyoid and ear ossicles belong to the axial skeleton, but they are not among the 22 skull bones.
Quick Recall: tap to check
How many bones form the cranium?
Eight cranial bones.
Name the U-shaped bone at the base of the buccal cavity.
The hyoid.
In Figure 2, which region lies just above the sacrum?
The lumbar region (5 lumbar vertebrae).
Through which part of a vertebra does the spinal cord pass?
The neural canal.

2.3 Sternum and ribs

  • Sternum: a flat bone on the ventral midline of the thorax.
  • There are 12 pairs of ribs. Each rib is a thin flat bone.
  • Each rib is connected dorsally to the vertebral column and ventrally to the sternum.
  • ★ Exam imp A rib has two articulation surfaces on its dorsal end, so it is called bicephalic.

Types of ribs

TypePairsConnection
True ribsFirst 7 pairs (1st-7th)Dorsally attached to the thoracic vertebrae; ventrally connected to the sternum with the help of hyaline cartilage
Vertebrochondral (false) ribs8th, 9th and 10th pairsDo not articulate directly with the sternum; join the seventh rib with the help of hyaline cartilage
Floating ribsLast 2 pairs (11th and 12th)Not connected ventrally
  • The thoracic vertebrae, ribs and sternum together form the rib cage.
Ribs and rib cage, front view Front view of the rib cage. Twelve pairs of ribs curve forwards from the vertebral column at the back. The upper seven pairs, the true ribs, join the sternum in the midline through bars of cartilage. The eighth, ninth and tenth pairs, the false ribs, join the cartilage of the seventh rib. The eleventh and twelfth pairs, the floating ribs, are short and end freely in front. Trueribs Falseribs Floatingribs 1 2 3 4 5 6 7 8 9 10 11 12 Ribs Sternum Hyalinecartilage Vertebralcolumn
Figure 3: Ribs and rib cage. Ribs 1 to 7 (true ribs) reach the sternum, ribs 8 to 10 (false ribs) join the seventh rib through cartilage, and ribs 11 and 12 (floating ribs) are free at their front ends.
Memory Trick

Ribs 7-3-2: 7 True pairs, 3 False pairs, 2 Floating pairs = 12 pairs.

★ Very important Each rib is bicephalic: it has two articulation surfaces on its dorsal end. Only the first 7 pairs reach the sternum directly; pairs 8-10 join the 7th rib; pairs 11-12 float.
Key idea
The 80 axial bones are the skull (22), hyoid (1), ear ossicles (6), vertebrae (26), sternum (1) and ribs (24).

3. Appendicular Skeleton

  • The bones of the limbs along with their girdles form the appendicular skeleton.
★ Very important Each limb is made of 30 bones. The limbs articulate with the axial skeleton through the pectoral and pelvic girdles.

3.1 Bones of the limbs

PartFore limb (hand)Hind limb (leg)
Upper arm or thighHumerusFemur (thigh bone, the longest bone)
Forearm or lower legRadius and ulnaTibia and fibula
Wrist or ankleCarpals (wrist bones): 8Tarsals (ankle bones): 7
Palm or soleMetacarpals (palm bones): 5Metatarsals: 5
DigitsPhalanges: 14Phalanges: 14
Knee capNonePatella: 1
Total3030
  • Patella: a cup-shaped bone that covers the knee ventrally; it is the knee cap.
  • ★ Exam imp The femur (thigh bone) is the longest bone.
Tips and Tricks

Hand and leg counts differ in only two places: 8 carpals but 7 tarsals, and the leg has the extra patella. That is why both limbs still total 30 bones.

Count check for the whole skeleton: 4 limbs × 30 = 120, plus 4 pectoral girdle bones and 2 coxal bones = 126; and 126 + 80 = 206.

3.2 Girdles

  • The pectoral and pelvic girdle bones help the upper and the lower limbs to articulate with the axial skeleton.
  • Each girdle is formed of two halves.

3.3 Pectoral girdle

  • Each half of the pectoral girdle consists of a clavicle and a scapula.
  • ★ Exam imp Scapula: a large triangular flat bone in the dorsal part of the thorax, between the second and the seventh ribs.
  • The dorsal, flat, triangular body of the scapula has a slightly elevated ridge called the spine.
  • The spine projects as a flat, expanded process called the acromion. The clavicle articulates with the acromion.
  • Below the acromion is a depression, the glenoid cavity. It articulates with the head of the humerus to form the shoulder joint.
  • Clavicle: a long slender bone with two curvatures, commonly called the collar bone.
Right pectoral girdle and upper limb, front view Front view of the bones of the right shoulder and arm. The clavicle runs across the top of the shoulder to meet the scapula. The humerus of the upper arm hangs from the shoulder joint, followed by the radius and ulna of the forearm, a cluster of carpals at the wrist, the metacarpals of the palm and the phalanges of the fingers and thumb. Clavicle Scapula Humerus Ulna Radius Carpals Metacarpals Phalanges
Figure 4: Right pectoral girdle and upper limb (front view). The clavicle and scapula form the girdle; the humerus, radius and ulna, carpals, metacarpals and phalanges form the limb.

3.4 Pelvic girdle

  • The pelvic girdle consists of two coxal bones.
  • ★ Exam imp Each coxal bone is formed by the fusion of three bones: ilium, ischium and pubis.
  • At the point of fusion of these bones is a cavity, the acetabulum, to which the thigh bone articulates.
  • The two halves of the pelvic girdle meet ventrally to form the pubic symphysis, which contains fibrous cartilage.
Right pelvic girdle and lower limb bones, front view Front view of the bones of the right hip and leg. The coxal bone, made of the ilium above and the pubis and ischium below, meets the sacrum at the back. The head of the femur fits into the hip socket. The patella lies in front of the knee, the tibia and the thinner fibula, on the outer side, form the lower leg, and the tarsals, metatarsals and phalanges form the foot. Coxal bone Femur Fibula Ilium Sacrum Pubis Ischium Patella Tibia Tarsals Metatarsals Phalanges
Figure 5: Right pelvic girdle and lower limb bones (front view). The coxal bone (ilium, ischium and pubis) meets the femur at the acetabulum; below come the patella, tibia and fibula, tarsals, metatarsals and phalanges.

Pectoral and pelvic girdles compared

FeaturePectoral girdlePelvic girdle
Limb servedUpper limb (fore limb)Lower limb (hind limb)
Each halfClavicle + scapulaOne coxal bone (ilium + ischium + pubis, fused)
Cavity for the limb boneGlenoid cavity, for the head of the humerusAcetabulum, for the thigh bone (femur)
Joint formedShoulder jointArticulation of the thigh bone at the acetabulum
Special featureScapula has a spine that ends as the acromion; the clavicle is the collar boneThe two halves meet ventrally at the pubic symphysis (fibrous cartilage)
Memory Trick

Coxal bone = I, I, P: Ilium, Ischium, Pubis, fused around the acetabulum.

Glenoid goes with the arm (shoulder); Acetabulum goes with the leg (hip). Clavicle meets the Acromion.

NEET Focus
  • The clavicle articulates with the acromion; the head of the humerus fits the glenoid cavity. Do not swap these.
  • The acetabulum is formed where the ilium, ischium and pubis fuse; it is part of the pelvic girdle, not the femur.
Quick Recall: tap to check
In Figure 4, which two bones form one half of the pectoral girdle?
The clavicle and the scapula.
Name the process of the scapula with which the clavicle articulates.
The acromion.
In Figure 5, which three bones fuse to form the coxal bone?
Ilium, ischium and pubis.
What does the pubic symphysis contain?
Fibrous cartilage.
Key idea
Each limb has 30 bones and joins the axial skeleton through a girdle: clavicle and scapula above, coxal bones below.

4. Exam Essentials

Pairs to Match

Bone or structureFeature
Cranial bones8; form the cranium
Facial bones14; front part of the skull
HyoidSingle U-shaped bone at the base of the buccal cavity
Malleus, incus and stapesEar ossicles of the middle ear
Occipital condylesArticulate with the atlas; dicondylic skull
AtlasFirst vertebra
True ribs1st to 7th pairs
Vertebrochondral (false) ribs8th, 9th and 10th pairs
Floating ribs11th and 12th pairs
FemurThigh bone; the longest bone
PatellaKnee cap
AcromionArticulates with the clavicle
Glenoid cavityArticulates with the head of the humerus
AcetabulumArticulates with the thigh bone
Pubic symphysisContains fibrous cartilage
Exceptions
  • Not every rib reaches the sternum directly: pairs 8-10 join the seventh rib, and pairs 11-12 are not connected ventrally.
  • The hyoid and the ear ossicles are axial bones but are not counted among the 22 skull bones.
  • The sacrum and coccyx are each counted as one vertebra because each is fused.
  • The leg has 7 tarsals, unlike the 8 carpals of the hand; the patella brings the leg total to 30.
  • Seven cervical vertebrae are found in almost all mammals, not in every mammal.
  • The clavicle articulates with the acromion, not with the glenoid cavity.
  • Cartilage has a pliable matrix (chondroitin salts), unlike the hard matrix of bone (calcium salts).

Numbers to Remember

  • Bones in the human skeleton: 206; axial skeleton: 80.
  • Skull: 22 (8 cranial + 14 facial); ear ossicles: 3 in each middle ear.
  • Vertebrae: 26 = 7 cervical + 12 thoracic + 5 lumbar + 1 sacral + 1 coccygeal.
  • Ribs: 12 pairs = 7 true + 3 false + 2 floating.
  • Bones in each limb: 30; carpals 8, tarsals 7, metacarpals and metatarsals 5 each, phalanges 14 in each limb.
  • Scapula lies between the 2nd and the 7th ribs; the clavicle has 2 curvatures.
  • Occipital condyles: 2; bones fused in each coxal bone: 3.

5. Quick Revision

  • Skeletal system: bones and a few cartilages; 206 bones in two divisions, axial and appendicular.
  • Bone matrix is hard (calcium salts); cartilage matrix is pliable (chondroitin salts).
  • Axial skeleton: 80 bones: skull, vertebral column, sternum, ribs (with hyoid and ear ossicles).
  • Skull: 22 bones, 8 cranial (cranium) and 14 facial; hyoid is U-shaped; ear ossicles are malleus, incus, stapes.
  • Two occipital condyles articulate with the atlas: dicondylic skull.
  • Vertebral column: 26 vertebrae, dorsal; neural canal carries the spinal cord.
  • Regions: cervical 7, thoracic 12, lumbar 5, sacral 1 (fused), coccygeal 1 (fused).
  • Column protects the spinal cord, supports the head, and anchors the ribs and back muscles.
  • Sternum: flat bone on the ventral midline of the thorax.
  • 12 pairs of bicephalic ribs: true 1-7, vertebrochondral (false) 8-10, floating 11-12.
  • Rib cage: thoracic vertebrae, ribs and sternum.
  • Each limb: 30 bones. Fore limb: humerus, radius, ulna, 8 carpals, 5 metacarpals, 14 phalanges.
  • Hind limb: femur (longest), tibia, fibula, 7 tarsals, 5 metatarsals, 14 phalanges, patella.
  • Pectoral girdle: clavicle (collar bone) and scapula (spine, acromion, glenoid cavity).
  • Pelvic girdle: two coxal bones (ilium, ischium, pubis); acetabulum; pubic symphysis with fibrous cartilage.

6. Solved Examples

Solved Example 1
Match the regions of the human vertebral column (List I) with the number of vertebrae (List II).
List I: A. Cervical, B. Thoracic, C. Lumbar, D. Sacral
List II: I. 12, II. 1 (fused), III. 7, IV. 5
Choose the correct answer:
(A) A-I, B-III, C-IV, D-II
(B) A-III, B-I, C-IV, D-II
(C) A-III, B-IV, C-I, D-II
(D) A-IV, B-I, C-III, D-II
Solution:

Answer: (B). Cervical 7 (III), thoracic 12 (I), lumbar 5 (IV), sacral 1 fused (II).

Solved Example 2
Read the statements about human ribs.
A. There are 12 pairs of ribs.
B. Each rib is bicephalic.
C. The 8th, 9th and 10th pairs articulate directly with the sternum.
D. The 11th and 12th pairs are floating ribs.
E. True ribs are joined to the sternum by fibrous cartilage.
Choose the correct answer:
(A) A, B and D only
(B) A, C and D only
(C) B, D and E only
(D) A, B, D and E only
Solution:

Answer: (A). C is wrong: pairs 8-10 join the seventh rib, not the sternum directly. E is wrong: true ribs join the sternum through hyaline cartilage.

Solved Example 3
Arrange the bones of the human fore limb from the shoulder to the fingertips.
A. Carpals
B. Humerus
C. Phalanges
D. Radius and ulna
E. Metacarpals
Choose the correct answer:
(A) B, D, E, A, C
(B) D, B, A, E, C
(C) B, D, A, E, C
(D) B, A, D, E, C
Solution:

Answer: (C). Humerus, then radius and ulna, then the carpals of the wrist, the metacarpals of the palm and the phalanges of the digits.

Solved Example 4
Which of the following is NOT a part of the axial skeleton?
(A) Sternum
(B) Hyoid
(C) Ear ossicles
(D) Clavicle
Solution:

Answer: (D). The clavicle belongs to the pectoral girdle, which is part of the appendicular skeleton.

Solved Example 5
The acetabulum is present at the point of fusion of:
(A) Clavicle and scapula
(B) Sacrum and coccyx
(C) Ilium, ischium and pubis
(D) Femur and patella
Solution:

Answer: (C). Each coxal bone forms by the fusion of the ilium, ischium and pubis; the acetabulum lies at their meeting point and receives the thigh bone.

Solved Example 6
Statement I: Each limb of a human being is made of 30 bones.
Statement II: The hind limb has 8 tarsals and a patella.
(A) Both Statement I and Statement II are correct
(B) Statement I is correct but Statement II is incorrect
(C) Statement I is incorrect but Statement II is correct
(D) Both Statement I and Statement II are incorrect
Solution:

Answer: (B). The hind limb has 7 tarsals; with the femur, tibia, fibula, 5 metatarsals, 14 phalanges and the patella it totals 30.

7. Practice Questions

Practice Questions
  1. Match List I with List II.
    List I: A. Scapula, B. Clavicle, C. Coxal bone, D. Patella
    List II: I. Knee cap, II. Collar bone, III. Large triangular flat bone in the dorsal thorax, IV. Fusion of ilium, ischium and pubis
    Choose the correct answer:
    (A) A-II, B-III, C-IV, D-I
    (B) A-III, B-IV, C-II, D-I
    (C) A-III, B-II, C-IV, D-I
    (D) A-I, B-II, C-IV, D-IIIAnswer: (C). Scapula-III, clavicle-II, coxal bone-IV, patella-I.
  2. Read the statements about the human skull.
    A. The skull has 22 bones.
    B. There are 14 cranial bones.
    C. The hyoid is a U-shaped bone at the base of the buccal cavity.
    D. The human skull is monocondylic.
    E. Each middle ear has three ear ossicles.
    Choose the correct answer:
    (A) A, B and C only
    (B) A, C and E only
    (C) C, D and E only
    (D) A, B, C and E onlyAnswer: (B). There are 8 cranial bones (B wrong), and the skull has two occipital condyles, so it is dicondylic (D wrong).
  3. Arrange the regions of the vertebral column starting from the skull.
    A. Lumbar
    B. Sacral
    C. Cervical
    D. Coccygeal
    E. Thoracic
    Choose the correct answer:
    (A) C, A, E, B, D
    (B) E, C, A, B, D
    (C) C, E, B, A, D
    (D) C, E, A, B, DAnswer: (D). Cervical, thoracic, lumbar, sacral, coccygeal.
  4. Which of the following is NOT correct about the scapula?
    (A) It is a large triangular flat bone
    (B) It lies in the dorsal part of the thorax between the second and the seventh ribs
    (C) Its spine projects as the acromion
    (D) Its glenoid cavity articulates with the femurAnswer: (D). The glenoid cavity articulates with the head of the humerus; the femur fits into the acetabulum.
  5. True or false? Correct the false statements. (a) The human skeleton has 206 bones. (b) There are 11 pairs of ribs in man. (c) The sternum is present on the ventral side of the body.Answer: (a) True. (b) False: there are 12 pairs of ribs. (c) True: the sternum lies on the ventral midline of the thorax.
  6. Write the differences between the pectoral and the pelvic girdle.Answer: Pectoral girdle: joins the upper limb; each half has a clavicle and a scapula; the glenoid cavity receives the head of the humerus (shoulder joint). Pelvic girdle: joins the lower limb; two coxal bones, each from fused ilium, ischium and pubis; the acetabulum receives the femur; the halves meet ventrally at the pubic symphysis.
  7. Fill in the blanks. (a) All mammals (except a few) have ____ cervical vertebrae. (b) The number of phalanges in each limb of a human being is ____. (c) The ____ and ____ pairs of ribs are called floating ribs. (d) The human cranium is made of ____ bones.Answer: (a) Seven. (b) 14. (c) 11th and 12th. (d) Eight.

Common Mistakes to Avoid

Watch out
  • Adding the hyoid and ear ossicles to the 22 skull bones. Correct: they are counted separately within the 80 axial bones.
  • Writing 33 vertebrae for the human adult. Correct: 26, because the sacrum and the coccyx are each one fused unit.
  • Saying false ribs join the sternum directly. Correct: pairs 8-10 join the seventh rib through hyaline cartilage.
  • Confusing the glenoid cavity with the acetabulum. Correct: the glenoid cavity (scapula) takes the humerus; the acetabulum (coxal bone) takes the femur.
  • Writing 8 tarsals. Correct: 8 carpals in the hand, 7 tarsals in the ankle.
  • Forgetting the patella when counting the 30 bones of the hind limb.
  • Calling the atlas the second vertebra. Correct: it is the first vertebra and articulates with the occipital condyles.
  • Saying the clavicle articulates with the glenoid cavity. Correct: it articulates with the acromion.

Frequently Asked Questions

How many bones are there in the human skeleton?

The human skeleton has 206 bones and a few cartilages. It has two divisions: the axial skeleton of 80 bones along the main axis of the body, and the appendicular skeleton of the limb bones and their girdles. Bone has a hard matrix of calcium salts, while cartilage has a pliable matrix of chondroitin salts.

Which bones form the axial skeleton?

The axial skeleton has 80 bones: the 22 skull bones, the hyoid, the six ear ossicles, the 26 vertebrae, the sternum and the 24 ribs. These lie along the main axis of the body. The skull, vertebral column, sternum and ribs are the four main parts of the axial skeleton.

What is meant by a dicondylic skull?

A dicondylic skull is one that articulates with the vertebral column through two occipital condyles. In human beings, the two occipital condyles at the base of the skull articulate with the atlas, the first vertebra. This is how the skull joins the superior region of the vertebral column.

How many vertebrae are there in the human vertebral column?

The human vertebral column has 26 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 1 sacral and 1 coccygeal. The sacral and coccygeal vertebrae are each a single fused unit. The column protects the spinal cord, supports the head and gives attachment to the ribs and back muscles.

What are true, false and floating ribs?

True ribs are the first seven pairs, joined to the sternum by hyaline cartilage. False or vertebrochondral ribs are the 8th, 9th and 10th pairs, which join the seventh rib instead of the sternum. Floating ribs are the 11th and 12th pairs, which are not connected ventrally at all.

Why are ribs called bicephalic?

Ribs are called bicephalic because each rib has two articulation surfaces on its dorsal end, where it joins the vertebral column. There are 12 pairs of ribs; each is a thin flat bone joined dorsally to the vertebral column and, except for the floating ribs, ventrally to the sternum directly or indirectly.

How do 30 bones make up each human limb?

The fore limb has the humerus, radius, ulna, 8 carpals, 5 metacarpals and 14 phalanges, which make 30. The hind limb has the femur, tibia, fibula, 7 tarsals, 5 metatarsals, 14 phalanges and the patella, which also make 30. The extra patella balances the one tarsal fewer.

What is the difference between the pectoral and pelvic girdles?

The pectoral girdle joins the upper limb to the axial skeleton; each half has a clavicle and a scapula, and the glenoid cavity receives the humerus. The pelvic girdle joins the lower limb; it has two coxal bones of fused ilium, ischium and pubis, with an acetabulum that receives the femur.

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